#ifndef DATE_H
#define DATE_H

// The MIT License (MIT)
//
// Copyright (c) 2015, 2016, 2017 Howard Hinnant
// Copyright (c) 2016 Adrian Colomitchi
// Copyright (c) 2017 Florian Dang
// Copyright (c) 2017 Paul Thompson
// Copyright (c) 2018, 2019 Tomasz Kamiński
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
// Our apologies.  When the previous paragraph was written, lowercase had not yet
// been invented (that would involve another several millennia of evolution).
// We did not mean to shout.

#ifndef HAS_STRING_VIEW
#  if __cplusplus >= 201703 || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
#    define HAS_STRING_VIEW 1
#  else
#    define HAS_STRING_VIEW 0
#  endif
#endif  // HAS_STRING_VIEW

#include <cassert>
#include <algorithm>
#include <cctype>
#include <chrono>
#include <climits>
#if !(__cplusplus >= 201402)
#  include <cmath>
#endif
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <ctime>
#include <ios>
#include <istream>
#include <iterator>
#include <limits>
#include <locale>
#include <memory>
#include <ostream>
#include <ratio>
#include <sstream>
#include <stdexcept>
#include <string>
#if HAS_STRING_VIEW
# include <string_view>
#endif
#include <utility>
#include <type_traits>

#ifdef __GNUC__
# pragma GCC diagnostic push
# if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR > 7)
#  pragma GCC diagnostic ignored "-Wpedantic"
# endif
# if __GNUC__ < 5
// GCC 4.9 Bug 61489 Wrong warning with -Wmissing-field-initializers
#  pragma GCC diagnostic ignored "-Wmissing-field-initializers"
# endif
#endif

#ifdef _MSC_VER
#   pragma warning(push)
// warning C4127: conditional expression is constant
#   pragma warning(disable : 4127)
#endif

namespace date {

//---------------+
// Configuration |
//---------------+

#ifndef ONLY_C_LOCALE
#  define ONLY_C_LOCALE 0
#endif

#if defined(_MSC_VER) && (!defined(__clang__) || (_MSC_VER < 1910))
// MSVC
#  ifndef _SILENCE_CXX17_UNCAUGHT_EXCEPTION_DEPRECATION_WARNING
#    define _SILENCE_CXX17_UNCAUGHT_EXCEPTION_DEPRECATION_WARNING
#  endif
#  if _MSC_VER < 1910
//   before VS2017
#    define CONSTDATA const
#    define CONSTCD11
#    define CONSTCD14
#    define NOEXCEPT _NOEXCEPT
#  else
//   VS2017 and later
#    define CONSTDATA constexpr const
#    define CONSTCD11 constexpr
#    define CONSTCD14 constexpr
#    define NOEXCEPT noexcept
#  endif

#elif defined(__SUNPRO_CC) && __SUNPRO_CC <= 0x5150
// Oracle Developer Studio 12.6 and earlier
#  define CONSTDATA constexpr const
#  define CONSTCD11 constexpr
#  define CONSTCD14
#  define NOEXCEPT noexcept

#elif __cplusplus >= 201402
// C++14
#  define CONSTDATA constexpr const
#  define CONSTCD11 constexpr
#  define CONSTCD14 constexpr
#  define NOEXCEPT noexcept
#else
// C++11
#  define CONSTDATA constexpr const
#  define CONSTCD11 constexpr
#  define CONSTCD14
#  define NOEXCEPT noexcept
#endif

#ifndef HAS_UNCAUGHT_EXCEPTIONS
#  if __cplusplus > 201703
#    define HAS_UNCAUGHT_EXCEPTIONS 1
#  else
#    define HAS_UNCAUGHT_EXCEPTIONS 0
#  endif
#endif  // HAS_UNCAUGHT_EXCEPTIONS

#ifndef HAS_VOID_T
#  if __cplusplus >= 201703
#    define HAS_VOID_T 1
#  else
#    define HAS_VOID_T 0
#  endif
#endif  // HAS_VOID_T

// Protect from Oracle sun macro
#ifdef sun
#  undef sun
#endif

//-----------+
// Interface |
//-----------+

// durations

using days = std::chrono::duration
             <int, std::ratio_multiply<std::ratio<24>, std::chrono::hours::period>::type>;

using weeks = std::chrono::duration
              <int, std::ratio_multiply<std::ratio<7>, days::period>::type>;

using years = std::chrono::duration
              <int, std::ratio_multiply<std::ratio<146097, 400>, days::period>::type>;

using months = std::chrono::duration
               <int, std::ratio_divide<years::period, std::ratio<12>>::type>;

// time_point

template <class Duration>
using sys_time = std::chrono::time_point<std::chrono::system_clock, Duration>;

using sys_days    = sys_time<days>;
using sys_seconds = sys_time<std::chrono::seconds>;

struct local_t {};

template <class Duration>
using local_time = std::chrono::time_point<local_t, Duration>;

using local_seconds = local_time<std::chrono::seconds>;
using local_days    = local_time<days>;

// types

struct last_spec {
  explicit last_spec() = default;
};

class day;
class month;
class year;

class weekday;
class weekday_indexed;
class weekday_last;

class month_day;
class month_day_last;
class month_weekday;
class month_weekday_last;

class year_month;

class year_month_day;
class year_month_day_last;
class year_month_weekday;
class year_month_weekday_last;

// date composition operators

CONSTCD11 year_month operator/(const year &y, const month &m) NOEXCEPT;
CONSTCD11 year_month operator/(const year &y, int          m) NOEXCEPT;

CONSTCD11 month_day operator/(const day &d, const month &m) NOEXCEPT;
CONSTCD11 month_day operator/(const day &d, int          m) NOEXCEPT;
CONSTCD11 month_day operator/(const month &m, const day &d) NOEXCEPT;
CONSTCD11 month_day operator/(const month &m, int        d) NOEXCEPT;
CONSTCD11 month_day operator/(int          m, const day &d) NOEXCEPT;

CONSTCD11 month_day_last operator/(const month &m, last_spec) NOEXCEPT;
CONSTCD11 month_day_last operator/(int          m, last_spec) NOEXCEPT;
CONSTCD11 month_day_last operator/(last_spec, const month &m) NOEXCEPT;
CONSTCD11 month_day_last operator/(last_spec, int          m) NOEXCEPT;

CONSTCD11 month_weekday operator/(const month &m,
                                  const weekday_indexed &wdi) NOEXCEPT;
CONSTCD11 month_weekday operator/(int          m,
                                  const weekday_indexed &wdi) NOEXCEPT;
CONSTCD11 month_weekday operator/(const weekday_indexed &wdi,
                                  const month &m) NOEXCEPT;
CONSTCD11 month_weekday operator/(const weekday_indexed &wdi,
                                  int          m) NOEXCEPT;

CONSTCD11 month_weekday_last operator/(const month &m,
                                       const weekday_last &wdl) NOEXCEPT;
CONSTCD11 month_weekday_last operator/(int          m,
                                       const weekday_last &wdl) NOEXCEPT;
CONSTCD11 month_weekday_last operator/(const weekday_last &wdl,
                                       const month &m) NOEXCEPT;
CONSTCD11 month_weekday_last operator/(const weekday_last &wdl,
                                       int          m) NOEXCEPT;

CONSTCD11 year_month_day operator/(const year_month &ym, const day &d) NOEXCEPT;
CONSTCD11 year_month_day operator/(const year_month &ym, int        d) NOEXCEPT;
CONSTCD11 year_month_day operator/(const year &y, const month_day &md) NOEXCEPT;
CONSTCD11 year_month_day operator/(int         y, const month_day &md) NOEXCEPT;
CONSTCD11 year_month_day operator/(const month_day &md, const year &y) NOEXCEPT;
CONSTCD11 year_month_day operator/(const month_day &md, int         y) NOEXCEPT;

CONSTCD11
year_month_day_last operator/(const year_month &ym,   last_spec) NOEXCEPT;
CONSTCD11
year_month_day_last operator/(const year &y,
                              const month_day_last &mdl) NOEXCEPT;
CONSTCD11
year_month_day_last operator/(int         y,
                              const month_day_last &mdl) NOEXCEPT;
CONSTCD11
year_month_day_last operator/(const month_day_last &mdl,
                              const year &y) NOEXCEPT;
CONSTCD11
year_month_day_last operator/(const month_day_last &mdl,
                              int         y) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(const year_month &ym, const weekday_indexed &wdi) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(const year        &y, const month_weekday   &mwd) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(int                y, const month_weekday   &mwd) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(const month_weekday &mwd, const year          &y) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(const month_weekday &mwd, int                  y) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(const year_month &ym, const weekday_last &wdl) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(const year &y, const month_weekday_last &mwdl) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(int         y, const month_weekday_last &mwdl) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(const month_weekday_last &mwdl, const year &y) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(const month_weekday_last &mwdl, int         y) NOEXCEPT;

// Detailed interface

// day

class day {
  unsigned char d_;

public:
  day() = default;
  explicit CONSTCD11 day(unsigned d) NOEXCEPT;

  CONSTCD14 day &operator++()    NOEXCEPT;
  CONSTCD14 day  operator++(int) NOEXCEPT;
  CONSTCD14 day &operator--()    NOEXCEPT;
  CONSTCD14 day  operator--(int) NOEXCEPT;

  CONSTCD14 day &operator+=(const days &d) NOEXCEPT;
  CONSTCD14 day &operator-=(const days &d) NOEXCEPT;

  CONSTCD11 explicit operator unsigned() const NOEXCEPT;
  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator!=(const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator< (const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator> (const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator<=(const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator>=(const day &x, const day &y) NOEXCEPT;

CONSTCD11 day  operator+(const day  &x, const days &y) NOEXCEPT;
CONSTCD11 day  operator+(const days &x, const day  &y) NOEXCEPT;
CONSTCD11 day  operator-(const day  &x, const days &y) NOEXCEPT;
CONSTCD11 days operator-(const day  &x, const day  &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const day &d);

// month

class month {
  unsigned char m_;

public:
  month() = default;
  explicit CONSTCD11 month(unsigned m) NOEXCEPT;

  CONSTCD14 month &operator++()    NOEXCEPT;
  CONSTCD14 month  operator++(int) NOEXCEPT;
  CONSTCD14 month &operator--()    NOEXCEPT;
  CONSTCD14 month  operator--(int) NOEXCEPT;

  CONSTCD14 month &operator+=(const months &m) NOEXCEPT;
  CONSTCD14 month &operator-=(const months &m) NOEXCEPT;

  CONSTCD11 explicit operator unsigned() const NOEXCEPT;
  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator!=(const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator< (const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator> (const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator<=(const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator>=(const month &x, const month &y) NOEXCEPT;

CONSTCD14 month  operator+(const month  &x, const months &y) NOEXCEPT;
CONSTCD14 month  operator+(const months &x,  const month &y) NOEXCEPT;
CONSTCD14 month  operator-(const month  &x, const months &y) NOEXCEPT;
CONSTCD14 months operator-(const month  &x,  const month &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month &m);

// year

class year {
  short y_;

public:
  year() = default;
  explicit CONSTCD11 year(int y) NOEXCEPT;

  CONSTCD14 year &operator++()    NOEXCEPT;
  CONSTCD14 year  operator++(int) NOEXCEPT;
  CONSTCD14 year &operator--()    NOEXCEPT;
  CONSTCD14 year  operator--(int) NOEXCEPT;

  CONSTCD14 year &operator+=(const years &y) NOEXCEPT;
  CONSTCD14 year &operator-=(const years &y) NOEXCEPT;

  CONSTCD11 year operator-() const NOEXCEPT;
  CONSTCD11 year operator+() const NOEXCEPT;

  CONSTCD11 bool is_leap() const NOEXCEPT;

  CONSTCD11 explicit operator int() const NOEXCEPT;
  CONSTCD11 bool ok() const NOEXCEPT;

  static CONSTCD11 year min() NOEXCEPT { return year{-32767}; }
  static CONSTCD11 year max() NOEXCEPT { return year{32767}; }
};

CONSTCD11 bool operator==(const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator!=(const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator< (const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator> (const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator<=(const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator>=(const year &x, const year &y) NOEXCEPT;

CONSTCD11 year  operator+(const year  &x, const years &y) NOEXCEPT;
CONSTCD11 year  operator+(const years &x, const year  &y) NOEXCEPT;
CONSTCD11 year  operator-(const year  &x, const years &y) NOEXCEPT;
CONSTCD11 years operator-(const year  &x, const year  &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year &y);

// weekday

class weekday {
  unsigned char wd_;
public:
  weekday() = default;
  explicit CONSTCD11 weekday(unsigned wd) NOEXCEPT;
  CONSTCD14 weekday(const sys_days &dp) NOEXCEPT;
  CONSTCD14 explicit weekday(const local_days &dp) NOEXCEPT;

  CONSTCD14 weekday &operator++()    NOEXCEPT;
  CONSTCD14 weekday  operator++(int) NOEXCEPT;
  CONSTCD14 weekday &operator--()    NOEXCEPT;
  CONSTCD14 weekday  operator--(int) NOEXCEPT;

  CONSTCD14 weekday &operator+=(const days &d) NOEXCEPT;
  CONSTCD14 weekday &operator-=(const days &d) NOEXCEPT;

  CONSTCD11 bool ok() const NOEXCEPT;

  CONSTCD11 unsigned c_encoding() const NOEXCEPT;
  CONSTCD11 unsigned iso_encoding() const NOEXCEPT;

  CONSTCD11 weekday_indexed operator[](unsigned index) const NOEXCEPT;
  CONSTCD11 weekday_last    operator[](last_spec)      const NOEXCEPT;

private:
  static CONSTCD14 unsigned char weekday_from_days(int z) NOEXCEPT;

  friend CONSTCD11 bool operator==(const weekday &x, const weekday &y) NOEXCEPT;
  friend CONSTCD14 days operator-(const weekday &x, const weekday &y) NOEXCEPT;
  friend CONSTCD14 weekday operator+(const weekday &x, const days &y) NOEXCEPT;
  template<class CharT, class Traits>
  friend std::basic_ostream<CharT, Traits> &
  operator<<(std::basic_ostream<CharT, Traits> &os, const weekday &wd);
  friend class weekday_indexed;
};

CONSTCD11 bool operator==(const weekday &x, const weekday &y) NOEXCEPT;
CONSTCD11 bool operator!=(const weekday &x, const weekday &y) NOEXCEPT;

CONSTCD14 weekday operator+(const weekday &x, const days    &y) NOEXCEPT;
CONSTCD14 weekday operator+(const days    &x, const weekday &y) NOEXCEPT;
CONSTCD14 weekday operator-(const weekday &x, const days    &y) NOEXCEPT;
CONSTCD14 days    operator-(const weekday &x, const weekday &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday &wd);

// weekday_indexed

class weekday_indexed {
  unsigned char wd_    : 4;
  unsigned char index_ : 4;

public:
  weekday_indexed() = default;
  CONSTCD11 weekday_indexed(const date::weekday &wd, unsigned index) NOEXCEPT;

  CONSTCD11 date::weekday weekday() const NOEXCEPT;
  CONSTCD11 unsigned index() const NOEXCEPT;
  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const weekday_indexed &x,
                          const weekday_indexed &y) NOEXCEPT;
CONSTCD11 bool operator!=(const weekday_indexed &x,
                          const weekday_indexed &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday_indexed &wdi);

// weekday_last

class weekday_last {
  date::weekday wd_;

public:
  explicit CONSTCD11 weekday_last(const date::weekday &wd) NOEXCEPT;

  CONSTCD11 date::weekday weekday() const NOEXCEPT;
  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const weekday_last &x,
                          const weekday_last &y) NOEXCEPT;
CONSTCD11 bool operator!=(const weekday_last &x,
                          const weekday_last &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday_last &wdl);

namespace detail {

struct unspecified_month_disambiguator {};

}  // namespace detail

// year_month

class year_month {
  date::year  y_;
  date::month m_;

public:
  year_month() = default;
  CONSTCD11 year_month(const date::year &y, const date::month &m) NOEXCEPT;

  CONSTCD11 date::year  year()  const NOEXCEPT;
  CONSTCD11 date::month month() const NOEXCEPT;

  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month & operator+=(const months &dm) NOEXCEPT;
  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month & operator-=(const months &dm) NOEXCEPT;
  CONSTCD14 year_month &operator+=(const years &dy) NOEXCEPT;
  CONSTCD14 year_month &operator-=(const years &dy) NOEXCEPT;

  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator!=(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator< (const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator> (const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator<=(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator>=(const year_month &x, const year_month &y) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month operator+(const year_month &ym, const months &dm) NOEXCEPT;
template<class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month operator+(const months &dm, const year_month &ym) NOEXCEPT;
template<class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month operator-(const year_month &ym, const months &dm) NOEXCEPT;

CONSTCD11 months operator-(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 year_month operator+(const year_month &ym, const years &dy) NOEXCEPT;
CONSTCD11 year_month operator+(const years &dy, const year_month &ym) NOEXCEPT;
CONSTCD11 year_month operator-(const year_month &ym, const years &dy) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month &ym);

// month_day

class month_day {
  date::month m_;
  date::day   d_;

public:
  month_day() = default;
  CONSTCD11 month_day(const date::month &m, const date::day &d) NOEXCEPT;

  CONSTCD11 date::month month() const NOEXCEPT;
  CONSTCD11 date::day   day() const NOEXCEPT;

  CONSTCD14 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator!=(const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator< (const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator> (const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator<=(const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator>=(const month_day &x, const month_day &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_day &md);

// month_day_last

class month_day_last {
  date::month m_;

public:
  CONSTCD11 explicit month_day_last(const date::month &m) NOEXCEPT;

  CONSTCD11 date::month month() const NOEXCEPT;
  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const month_day_last &x,
                          const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator!=(const month_day_last &x,
                          const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator< (const month_day_last &x,
                          const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator> (const month_day_last &x,
                          const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator<=(const month_day_last &x,
                          const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator>=(const month_day_last &x,
                          const month_day_last &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_day_last &mdl);

// month_weekday

class month_weekday {
  date::month           m_;
  date::weekday_indexed wdi_;
public:
  CONSTCD11 month_weekday(const date::month &m,
                          const date::weekday_indexed &wdi) NOEXCEPT;

  CONSTCD11 date::month           month()           const NOEXCEPT;
  CONSTCD11 date::weekday_indexed weekday_indexed() const NOEXCEPT;

  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const month_weekday &x,
                          const month_weekday &y) NOEXCEPT;
CONSTCD11 bool operator!=(const month_weekday &x,
                          const month_weekday &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_weekday &mwd);

// month_weekday_last

class month_weekday_last {
  date::month        m_;
  date::weekday_last wdl_;

public:
  CONSTCD11 month_weekday_last(const date::month &m,
                               const date::weekday_last &wd) NOEXCEPT;

  CONSTCD11 date::month        month()        const NOEXCEPT;
  CONSTCD11 date::weekday_last weekday_last() const NOEXCEPT;

  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11
bool operator==(const month_weekday_last &x,
                const month_weekday_last &y) NOEXCEPT;
CONSTCD11
bool operator!=(const month_weekday_last &x,
                const month_weekday_last &y) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const month_weekday_last &mwdl);

// class year_month_day

class year_month_day {
  date::year  y_;
  date::month m_;
  date::day   d_;

public:
  year_month_day() = default;
  CONSTCD11 year_month_day(const date::year &y, const date::month &m,
                           const date::day &d) NOEXCEPT;
  CONSTCD14 year_month_day(const year_month_day_last &ymdl) NOEXCEPT;

  CONSTCD14 year_month_day(sys_days dp) NOEXCEPT;
  CONSTCD14 explicit year_month_day(local_days dp) NOEXCEPT;

  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month_day & operator+=(const months &m) NOEXCEPT;
  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month_day & operator-=(const months &m) NOEXCEPT;
  CONSTCD14 year_month_day &operator+=(const years &y)  NOEXCEPT;
  CONSTCD14 year_month_day &operator-=(const years &y)  NOEXCEPT;

  CONSTCD11 date::year  year()  const NOEXCEPT;
  CONSTCD11 date::month month() const NOEXCEPT;
  CONSTCD11 date::day   day()   const NOEXCEPT;

  CONSTCD14 operator sys_days() const NOEXCEPT;
  CONSTCD14 explicit operator local_days() const NOEXCEPT;
  CONSTCD14 bool ok() const NOEXCEPT;

private:
  static CONSTCD14 year_month_day from_days(days dp) NOEXCEPT;
  CONSTCD14 days to_days() const NOEXCEPT;
};

CONSTCD11 bool operator==(const year_month_day &x,
                          const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator!=(const year_month_day &x,
                          const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator< (const year_month_day &x,
                          const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator> (const year_month_day &x,
                          const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator<=(const year_month_day &x,
                          const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator>=(const year_month_day &x,
                          const year_month_day &y) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month_day operator+(const year_month_day &ymd,
                                   const months &dm) NOEXCEPT;
template<class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month_day operator+(const months &dm,
                                   const year_month_day &ymd) NOEXCEPT;
template<class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month_day operator-(const year_month_day &ymd,
                                   const months &dm) NOEXCEPT;
CONSTCD11 year_month_day operator+(const year_month_day &ymd,
                                   const years &dy)  NOEXCEPT;
CONSTCD11 year_month_day operator+(const years &dy,
                                   const year_month_day &ymd)  NOEXCEPT;
CONSTCD11 year_month_day operator-(const year_month_day &ymd,
                                   const years &dy)  NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_day &ymd);

// year_month_day_last

class year_month_day_last {
  date::year           y_;
  date::month_day_last mdl_;

public:
  CONSTCD11 year_month_day_last(const date::year &y,
                                const date::month_day_last &mdl) NOEXCEPT;

  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month_day_last & operator+=(const months &m) NOEXCEPT;
  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month_day_last & operator-=(const months &m) NOEXCEPT;
  CONSTCD14 year_month_day_last &operator+=(const years &y)  NOEXCEPT;
  CONSTCD14 year_month_day_last &operator-=(const years &y)  NOEXCEPT;

  CONSTCD11 date::year           year()           const NOEXCEPT;
  CONSTCD11 date::month          month()          const NOEXCEPT;
  CONSTCD11 date::month_day_last month_day_last() const NOEXCEPT;
  CONSTCD14 date::day            day()            const NOEXCEPT;

  CONSTCD14 operator sys_days() const NOEXCEPT;
  CONSTCD14 explicit operator local_days() const NOEXCEPT;
  CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11
bool operator==(const year_month_day_last &x,
                const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator!=(const year_month_day_last &x,
                const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator< (const year_month_day_last &x,
                const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator> (const year_month_day_last &x,
                const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator<=(const year_month_day_last &x,
                const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator>=(const year_month_day_last &x,
                const year_month_day_last &y) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_day_last
operator+(const year_month_day_last &ymdl, const months &dm) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_day_last
operator+(const months &dm, const year_month_day_last &ymdl) NOEXCEPT;

CONSTCD11
year_month_day_last
operator+(const year_month_day_last &ymdl, const years &dy) NOEXCEPT;

CONSTCD11
year_month_day_last
operator+(const years &dy, const year_month_day_last &ymdl) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_day_last
operator-(const year_month_day_last &ymdl, const months &dm) NOEXCEPT;

CONSTCD11
year_month_day_last
operator-(const year_month_day_last &ymdl, const years &dy) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const year_month_day_last &ymdl);

// year_month_weekday

class year_month_weekday {
  date::year            y_;
  date::month           m_;
  date::weekday_indexed wdi_;

public:
  year_month_weekday() = default;
  CONSTCD11 year_month_weekday(const date::year &y, const date::month &m,
                               const date::weekday_indexed &wdi) NOEXCEPT;
  CONSTCD14 year_month_weekday(const sys_days &dp) NOEXCEPT;
  CONSTCD14 explicit year_month_weekday(const local_days &dp) NOEXCEPT;

  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month_weekday & operator+=(const months &m) NOEXCEPT;
  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month_weekday & operator-=(const months &m) NOEXCEPT;
  CONSTCD14 year_month_weekday &operator+=(const years &y)  NOEXCEPT;
  CONSTCD14 year_month_weekday &operator-=(const years &y)  NOEXCEPT;

  CONSTCD11 date::year year() const NOEXCEPT;
  CONSTCD11 date::month month() const NOEXCEPT;
  CONSTCD11 date::weekday weekday() const NOEXCEPT;
  CONSTCD11 unsigned index() const NOEXCEPT;
  CONSTCD11 date::weekday_indexed weekday_indexed() const NOEXCEPT;

  CONSTCD14 operator sys_days() const NOEXCEPT;
  CONSTCD14 explicit operator local_days() const NOEXCEPT;
  CONSTCD14 bool ok() const NOEXCEPT;

private:
  static CONSTCD14 year_month_weekday from_days(days dp) NOEXCEPT;
  CONSTCD14 days to_days() const NOEXCEPT;
};

CONSTCD11
bool operator==(const year_month_weekday &x,
                const year_month_weekday &y) NOEXCEPT;
CONSTCD11
bool operator!=(const year_month_weekday &x,
                const year_month_weekday &y) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_weekday
operator+(const year_month_weekday &ymwd, const months &dm) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_weekday
operator+(const months &dm, const year_month_weekday &ymwd) NOEXCEPT;

CONSTCD11
year_month_weekday
operator+(const year_month_weekday &ymwd, const years &dy) NOEXCEPT;

CONSTCD11
year_month_weekday
operator+(const years &dy, const year_month_weekday &ymwd) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_weekday
operator-(const year_month_weekday &ymwd, const months &dm) NOEXCEPT;

CONSTCD11
year_month_weekday
operator-(const year_month_weekday &ymwd, const years &dy) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const year_month_weekday &ymwdi);

// year_month_weekday_last

class year_month_weekday_last {
  date::year y_;
  date::month m_;
  date::weekday_last wdl_;

public:
  CONSTCD11 year_month_weekday_last(const date::year &y, const date::month &m,
                                    const date::weekday_last &wdl) NOEXCEPT;

  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month_weekday_last & operator+=(const months &m) NOEXCEPT;
  template<class = detail::unspecified_month_disambiguator>
  CONSTCD14 year_month_weekday_last & operator-=(const months &m) NOEXCEPT;
  CONSTCD14 year_month_weekday_last &operator+=(const years &y) NOEXCEPT;
  CONSTCD14 year_month_weekday_last &operator-=(const years &y) NOEXCEPT;

  CONSTCD11 date::year year() const NOEXCEPT;
  CONSTCD11 date::month month() const NOEXCEPT;
  CONSTCD11 date::weekday weekday() const NOEXCEPT;
  CONSTCD11 date::weekday_last weekday_last() const NOEXCEPT;

  CONSTCD14 operator sys_days() const NOEXCEPT;
  CONSTCD14 explicit operator local_days() const NOEXCEPT;
  CONSTCD11 bool ok() const NOEXCEPT;

private:
  CONSTCD14 days to_days() const NOEXCEPT;
};

CONSTCD11
bool
operator==(const year_month_weekday_last &x,
           const year_month_weekday_last &y) NOEXCEPT;

CONSTCD11
bool
operator!=(const year_month_weekday_last &x,
           const year_month_weekday_last &y) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_weekday_last
operator+(const year_month_weekday_last &ymwdl, const months &dm) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_weekday_last
operator+(const months &dm, const year_month_weekday_last &ymwdl) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator+(const year_month_weekday_last &ymwdl, const years &dy) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator+(const years &dy, const year_month_weekday_last &ymwdl) NOEXCEPT;

template<class = detail::unspecified_month_disambiguator>
CONSTCD14
year_month_weekday_last
operator-(const year_month_weekday_last &ymwdl, const months &dm) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator-(const year_month_weekday_last &ymwdl, const years &dy) NOEXCEPT;

template<class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const year_month_weekday_last &ymwdl);

#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
inline namespace literals {

CONSTCD11 date::day  operator "" _d(unsigned long long d) NOEXCEPT;
CONSTCD11 date::year operator "" _y(unsigned long long y) NOEXCEPT;

}  // inline namespace literals
#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)

// CONSTDATA date::month January{1};
// CONSTDATA date::month February{2};
// CONSTDATA date::month March{3};
// CONSTDATA date::month April{4};
// CONSTDATA date::month May{5};
// CONSTDATA date::month June{6};
// CONSTDATA date::month July{7};
// CONSTDATA date::month August{8};
// CONSTDATA date::month September{9};
// CONSTDATA date::month October{10};
// CONSTDATA date::month November{11};
// CONSTDATA date::month December{12};
//
// CONSTDATA date::weekday Sunday{0u};
// CONSTDATA date::weekday Monday{1u};
// CONSTDATA date::weekday Tuesday{2u};
// CONSTDATA date::weekday Wednesday{3u};
// CONSTDATA date::weekday Thursday{4u};
// CONSTDATA date::weekday Friday{5u};
// CONSTDATA date::weekday Saturday{6u};

#if HAS_VOID_T

template <class T, class = std::void_t<>>
struct is_clock
  : std::false_type {
};

template <class T>
struct is_clock<T, std::void_t<decltype(T::now()), typename T::rep, typename T::period,
       typename T::duration, typename T::time_point,
       decltype(T::is_steady)>>
       : std::true_type {
       };

#endif  // HAS_VOID_T

//----------------+
// Implementation |
//----------------+

// utilities
namespace detail {

template<class CharT, class Traits = std::char_traits<CharT>>
class save_istream {
protected:
  std::basic_ios<CharT, Traits> &is_;
  CharT fill_;
  std::ios::fmtflags flags_;
  std::streamsize width_;
  std::basic_ostream<CharT, Traits> *tie_;
  std::locale loc_;

public:
  ~save_istream()
  {
    is_.fill(fill_);
    is_.flags(flags_);
    is_.width(width_);
    is_.imbue(loc_);
    is_.tie(tie_);
  }

  save_istream(const save_istream &) = delete;
  save_istream &operator=(const save_istream &) = delete;

  explicit save_istream(std::basic_ios<CharT, Traits> &is)
    : is_(is)
    , fill_(is.fill())
    , flags_(is.flags())
    , width_(is.width(0))
    , tie_(is.tie(nullptr))
    , loc_(is.getloc())
  {
    if (tie_ != nullptr) {
      tie_->flush();
    }
  }
};

template<class CharT, class Traits = std::char_traits<CharT>>
class save_ostream
  : private save_istream<CharT, Traits> {
public:
  ~save_ostream()
  {
    if ((this->flags_ & std::ios::unitbuf) &&
#if HAS_UNCAUGHT_EXCEPTIONS
        std::uncaught_exceptions() == 0 &&
#else
        !std::uncaught_exception() &&
#endif
        this->is_.good()) {
      this->is_.rdbuf()->pubsync();
    }
  }

  save_ostream(const save_ostream &) = delete;
  save_ostream &operator=(const save_ostream &) = delete;

  explicit save_ostream(std::basic_ios<CharT, Traits> &os)
    : save_istream<CharT, Traits>(os)
  {
  }
};

template <class T>
struct choose_trunc_type {
  static const int digits = std::numeric_limits<T>::digits;
  using type = typename std::conditional
               <
               digits < 32,
               std::int32_t,
               typename std::conditional
               <
               digits < 64,
               std::int64_t,
#ifdef __SIZEOF_INT128__
               __int128
#else
               std::int64_t
#endif
               >::type
               >::type;
};

template <class T>
CONSTCD11
inline
typename std::enable_if
<
!std::chrono::treat_as_floating_point<T>::value,
T
>::type
trunc(T t) NOEXCEPT {
  return t;
}

template <class T>
CONSTCD14
inline
typename std::enable_if
<
std::chrono::treat_as_floating_point<T>::value,
    T
    >::type
trunc(T t) NOEXCEPT {
  using std::numeric_limits;
  using I = typename choose_trunc_type<T>::type;
  CONSTDATA auto digits = numeric_limits<T>::digits;
  static_assert(digits < numeric_limits<I>::digits, "");
  CONSTDATA auto max = I{1} << (digits - 1);
  CONSTDATA auto min = -max;
  const auto negative = t < T{0};
  if (min <= t && t <= max && t != 0 && t == t)
  {
    t = static_cast<T>(static_cast<I>(t));
    if (t == 0 && negative) {
      t = -t;
    }
  }
  return t;
}

template <std::intmax_t Xp, std::intmax_t Yp>
struct static_gcd {
  static const std::intmax_t value = static_gcd < Yp, Xp % Yp >::value;
};

template <std::intmax_t Xp>
struct static_gcd<Xp, 0> {
  static const std::intmax_t value = Xp;
};

template <>
struct static_gcd<0, 0> {
  static const std::intmax_t value = 1;
};

template <class R1, class R2>
struct no_overflow {
private:
  static const std::intmax_t gcd_n1_n2 = static_gcd<R1::num, R2::num>::value;
  static const std::intmax_t gcd_d1_d2 = static_gcd<R1::den, R2::den>::value;
  static const std::intmax_t n1 = R1::num / gcd_n1_n2;
  static const std::intmax_t d1 = R1::den / gcd_d1_d2;
  static const std::intmax_t n2 = R2::num / gcd_n1_n2;
  static const std::intmax_t d2 = R2::den / gcd_d1_d2;
  static const std::intmax_t max = INTMAX_MAX;

  template <std::intmax_t Xp, std::intmax_t Yp, bool overflow>
  struct mul {  // overflow == false
    static const std::intmax_t value = Xp * Yp;
  };

  template <std::intmax_t Xp, std::intmax_t Yp>
  struct mul<Xp, Yp, true> {
    static const std::intmax_t value = 1;
  };

public:
  static const bool value = (n1 <= max / d2) && (n2 <= max / d1);
  typedef std::ratio < mul < n1, d2, !value >::value,
          mul < n2, d1, !value >::value > type;
};

}  // detail

// trunc towards zero
template <class To, class Rep, class Period>
CONSTCD11
inline
typename std::enable_if
<
detail::no_overflow<Period, typename To::period>::value,
       To
       >::type
       trunc(const std::chrono::duration<Rep, Period> &d)
{
  return To{detail::trunc(std::chrono::duration_cast<To>(d).count())};
}

template <class To, class Rep, class Period>
CONSTCD11
inline
typename std::enable_if
<
!detail::no_overflow<Period, typename To::period>::value,
To
>::type
trunc(const std::chrono::duration<Rep, Period> &d)
{
  using std::chrono::duration_cast;
  using std::chrono::duration;
  using rep = typename std::common_type<Rep, typename To::rep>::type;
  return To{detail::trunc(duration_cast<To>(duration_cast<duration<rep>>(d)).count())};
}

#ifndef HAS_CHRONO_ROUNDING
#  if defined(_MSC_FULL_VER) && (_MSC_FULL_VER >= 190023918 || (_MSC_FULL_VER >= 190000000 && defined (__clang__)))
#    define HAS_CHRONO_ROUNDING 1
#  elif defined(__cpp_lib_chrono) && __cplusplus > 201402 && __cpp_lib_chrono >= 201510
#    define HAS_CHRONO_ROUNDING 1
#  elif defined(_LIBCPP_VERSION) && __cplusplus > 201402 && _LIBCPP_VERSION >= 3800
#    define HAS_CHRONO_ROUNDING 1
#  else
#    define HAS_CHRONO_ROUNDING 0
#  endif
#endif  // HAS_CHRONO_ROUNDING

#if HAS_CHRONO_ROUNDING == 0

// round down
template <class To, class Rep, class Period>
CONSTCD14
inline
typename std::enable_if
<
detail::no_overflow<Period, typename To::period>::value,
       To
       >::type
       floor(const std::chrono::duration<Rep, Period> &d)
{
  auto t = trunc<To>(d);
  if (t > d)
    return t - To{1};
  return t;
}

template <class To, class Rep, class Period>
CONSTCD14
inline
typename std::enable_if
<
!detail::no_overflow<Period, typename To::period>::value,
To
>::type
floor(const std::chrono::duration<Rep, Period> &d)
{
  using rep = typename std::common_type<Rep, typename To::rep>::type;
  return floor<To>(floor<std::chrono::duration<rep>>(d));
}

// round to nearest, to even on tie
template <class To, class Rep, class Period>
CONSTCD14
inline
To
round(const std::chrono::duration<Rep, Period> &d)
{
  auto t0 = floor<To>(d);
  auto t1 = t0 + To{1};
  if (t1 == To{0} && t0 < To{0})
    t1 = -t1;
  auto diff0 = d - t0;
  auto diff1 = t1 - d;
  if (diff0 == diff1) {
    if (t0 - trunc<To>(t0 / 2) * 2 == To{0})
      return t0;
    return t1;
  }
  if (diff0 < diff1) {
    return t0;
  }
  return t1;
}

// round up
template <class To, class Rep, class Period>
CONSTCD14
inline
To
ceil(const std::chrono::duration<Rep, Period> &d)
{
  auto t = trunc<To>(d);
  if (t < d)
    return t + To{1};
  return t;
}

template <class Rep, class Period,
          class = typename std::enable_if
          <
            std::numeric_limits<Rep>::is_signed
            >::type>
CONSTCD11
std::chrono::duration<Rep, Period>
abs(std::chrono::duration<Rep, Period> d)
{
  return d >= d.zero() ? d : -d;
}

// round down
template <class To, class Clock, class FromDuration>
CONSTCD11
inline
std::chrono::time_point<Clock, To>
floor(const std::chrono::time_point<Clock, FromDuration> &tp)
{
  using std::chrono::time_point;
  return time_point<Clock, To> {date::floor<To>(tp.time_since_epoch())};
}

// round to nearest, to even on tie
template <class To, class Clock, class FromDuration>
CONSTCD11
inline
std::chrono::time_point<Clock, To>
round(const std::chrono::time_point<Clock, FromDuration> &tp)
{
  using std::chrono::time_point;
  return time_point<Clock, To> {round<To>(tp.time_since_epoch())};
}

// round up
template <class To, class Clock, class FromDuration>
CONSTCD11
inline
std::chrono::time_point<Clock, To>
ceil(const std::chrono::time_point<Clock, FromDuration> &tp)
{
  using std::chrono::time_point;
  return time_point<Clock, To> {ceil<To>(tp.time_since_epoch())};
}

#else  // HAS_CHRONO_ROUNDING == 1

using std::chrono::floor;
using std::chrono::ceil;
using std::chrono::round;
using std::chrono::abs;

#endif  // HAS_CHRONO_ROUNDING

// trunc towards zero
template <class To, class Clock, class FromDuration>
CONSTCD11
inline
std::chrono::time_point<Clock, To>
trunc(const std::chrono::time_point<Clock, FromDuration> &tp)
{
  using std::chrono::time_point;
  return time_point<Clock, To> {trunc<To>(tp.time_since_epoch())};
}

// day

CONSTCD11 inline day::day(unsigned d) NOEXCEPT :
d_(static_cast<unsigned char>(d)) {}
CONSTCD14 inline day &day::operator++() NOEXCEPT {++d_; return *this;}
CONSTCD14 inline day day::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
CONSTCD14 inline day &day::operator--() NOEXCEPT {--d_; return *this;}
CONSTCD14 inline day day::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
CONSTCD14 inline day &day::operator+=(const days &d) NOEXCEPT {*this = *this + d; return *this;}
CONSTCD14 inline day &day::operator-=(const days &d) NOEXCEPT {*this = *this - d; return *this;}
CONSTCD11 inline day::operator unsigned() const NOEXCEPT
{
  return d_;
}
CONSTCD11 inline bool day::ok() const NOEXCEPT
{
  return 1 <= d_ && d_ <= 31;
}

CONSTCD11
inline
bool
operator==(const day &x, const day &y) NOEXCEPT {
  return static_cast<unsigned>(x) == static_cast<unsigned>(y);
}

CONSTCD11
inline
bool
operator!=(const day &x, const day &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD11
inline
bool
operator<(const day &x, const day &y) NOEXCEPT {
  return static_cast<unsigned>(x) < static_cast<unsigned>(y);
}

CONSTCD11
inline
bool
operator>(const day &x, const day &y) NOEXCEPT {
  return y < x;
}

CONSTCD11
inline
bool
operator<=(const day &x, const day &y) NOEXCEPT {
  return !(y < x);
}

CONSTCD11
inline
bool
operator>=(const day &x, const day &y) NOEXCEPT {
  return !(x < y);
}

CONSTCD11
inline
days
operator-(const day &x, const day &y) NOEXCEPT {
  return days{
    static_cast<days::rep>(static_cast<unsigned>(x)
                           - static_cast<unsigned>(y))};
}

CONSTCD11
inline
day
operator+(const day &x, const days &y) NOEXCEPT {
  return day{static_cast<unsigned>(x) + static_cast<unsigned>(y.count())};
}

CONSTCD11
inline
day
operator+(const days &x, const day &y) NOEXCEPT {
  return y + x;
}

CONSTCD11
inline
day
operator-(const day &x, const days &y) NOEXCEPT {
  return x + -y;
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const day &d)
{
  detail::save_ostream<CharT, Traits> _(os);
  os.fill('0');
  os.flags(std::ios::dec | std::ios::right);
  os.width(2);
  os << static_cast<unsigned>(d);
  if (!d.ok()) {
    os << " is not a valid day";
  }
  return os;
}

// month

CONSTCD11 inline month::month(unsigned m) NOEXCEPT :
m_(static_cast<decltype(m_)>(m)) {}
CONSTCD14 inline month &month::operator++() NOEXCEPT {*this += months{1}; return *this;}
CONSTCD14 inline month month::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
CONSTCD14 inline month &month::operator--() NOEXCEPT {*this -= months{1}; return *this;}
CONSTCD14 inline month month::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}

CONSTCD14
inline
month &
month::operator+=(const months &m) NOEXCEPT {
  *this = *this + m;
  return *this;
}

CONSTCD14
inline
month &
month::operator-=(const months &m) NOEXCEPT {
  *this = *this - m;
  return *this;
}

CONSTCD11 inline month::operator unsigned() const NOEXCEPT
{
  return m_;
}
CONSTCD11 inline bool month::ok() const NOEXCEPT
{
  return 1 <= m_ && m_ <= 12;
}

CONSTCD11
inline
bool
operator==(const month &x, const month &y) NOEXCEPT {
  return static_cast<unsigned>(x) == static_cast<unsigned>(y);
}

CONSTCD11
inline
bool
operator!=(const month &x, const month &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD11
inline
bool
operator<(const month &x, const month &y) NOEXCEPT {
  return static_cast<unsigned>(x) < static_cast<unsigned>(y);
}

CONSTCD11
inline
bool
operator>(const month &x, const month &y) NOEXCEPT {
  return y < x;
}

CONSTCD11
inline
bool
operator<=(const month &x, const month &y) NOEXCEPT {
  return !(y < x);
}

CONSTCD11
inline
bool
operator>=(const month &x, const month &y) NOEXCEPT {
  return !(x < y);
}

CONSTCD14
inline
months
operator-(const month &x, const month &y) NOEXCEPT {
  auto const d = static_cast<unsigned>(x) - static_cast<unsigned>(y);
  return months(d <= 11 ? d : d + 12);
}

CONSTCD14
inline
month
operator+(const month &x, const months &y) NOEXCEPT {
  auto const mu = static_cast<long long>(static_cast<unsigned>(x)) + (y.count() - 1);
  auto const yr = (mu >= 0 ? mu : mu - 11) / 12;
  return month{static_cast<unsigned>(mu - yr * 12 + 1)};
}

CONSTCD14
inline
month
operator+(const months &x, const month &y) NOEXCEPT {
  return y + x;
}

CONSTCD14
inline
month
operator-(const month &x, const months &y) NOEXCEPT {
  return x + -y;
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month &m)
{
  if (m.ok()) {
    CharT fmt[] = {'%', 'b', 0};
    os << format(os.getloc(), fmt, m);
  }
  else {
    os << static_cast<unsigned>(m) << " is not a valid month";
  }
  return os;
}

// year

CONSTCD11 inline year::year(int y) NOEXCEPT :
y_(static_cast<decltype(y_)>(y)) {}
CONSTCD14 inline year &year::operator++() NOEXCEPT {++y_; return *this;}
CONSTCD14 inline year year::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
CONSTCD14 inline year &year::operator--() NOEXCEPT {--y_; return *this;}
CONSTCD14 inline year year::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
CONSTCD14 inline year &year::operator+=(const years &y) NOEXCEPT {*this = *this + y; return *this;}
CONSTCD14 inline year &year::operator-=(const years &y) NOEXCEPT {*this = *this - y; return *this;}
CONSTCD11 inline year year::operator-() const NOEXCEPT
{
  return year{-y_};
}
CONSTCD11 inline year year::operator+() const NOEXCEPT
{
  return *this;
}

CONSTCD11
inline
bool
year::is_leap() const NOEXCEPT
{
  return y_ % 4 == 0 && (y_ % 100 != 0 || y_ % 400 == 0);
}

CONSTCD11 inline year::operator int() const NOEXCEPT
{
  return y_;
}

CONSTCD11
inline
bool
year::ok() const NOEXCEPT
{
  return y_ != std::numeric_limits<short>::min();
}

CONSTCD11
inline
bool
operator==(const year &x, const year &y) NOEXCEPT {
  return static_cast<int>(x) == static_cast<int>(y);
}

CONSTCD11
inline
bool
operator!=(const year &x, const year &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD11
inline
bool
operator<(const year &x, const year &y) NOEXCEPT {
  return static_cast<int>(x) < static_cast<int>(y);
}

CONSTCD11
inline
bool
operator>(const year &x, const year &y) NOEXCEPT {
  return y < x;
}

CONSTCD11
inline
bool
operator<=(const year &x, const year &y) NOEXCEPT {
  return !(y < x);
}

CONSTCD11
inline
bool
operator>=(const year &x, const year &y) NOEXCEPT {
  return !(x < y);
}

CONSTCD11
inline
years
operator-(const year &x, const year &y) NOEXCEPT {
  return years{static_cast<int>(x) - static_cast<int>(y)};
}

CONSTCD11
inline
year
operator+(const year &x, const years &y) NOEXCEPT {
  return year{static_cast<int>(x) + y.count()};
}

CONSTCD11
inline
year
operator+(const years &x, const year &y) NOEXCEPT {
  return y + x;
}

CONSTCD11
inline
year
operator-(const year &x, const years &y) NOEXCEPT {
  return year{static_cast<int>(x) - y.count()};
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year &y)
{
  detail::save_ostream<CharT, Traits> _(os);
  os.fill('0');
  os.flags(std::ios::dec | std::ios::internal);
  os.width(4 + (y < year{0}));
  os.imbue(std::locale::classic());
  os << static_cast<int>(y);
  if (!y.ok()) {
    os << " is not a valid year";
  }
  return os;
}

// weekday

CONSTCD14
inline
unsigned char
weekday::weekday_from_days(int z) NOEXCEPT {
  auto u = static_cast<unsigned>(z);
  return static_cast<unsigned char>(z >= -4 ? (u + 4) % 7 : u % 7);
}

CONSTCD11
inline
weekday::weekday(unsigned wd) NOEXCEPT
:
wd_(static_cast<decltype(wd_)>(wd != 7 ? wd : 0))
{}

CONSTCD14
inline
weekday::weekday(const sys_days &dp) NOEXCEPT
:
wd_(weekday_from_days(dp.time_since_epoch().count()))
{}

CONSTCD14
inline
weekday::weekday(const local_days &dp) NOEXCEPT
:
wd_(weekday_from_days(dp.time_since_epoch().count()))
{}

CONSTCD14 inline weekday &weekday::operator++() NOEXCEPT {*this += days{1}; return *this;}
CONSTCD14 inline weekday weekday::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
CONSTCD14 inline weekday &weekday::operator--() NOEXCEPT {*this -= days{1}; return *this;}
CONSTCD14 inline weekday weekday::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}

CONSTCD14
inline
weekday &
weekday::operator+=(const days &d) NOEXCEPT {
  *this = *this + d;
  return *this;
}

CONSTCD14
inline
weekday &
weekday::operator-=(const days &d) NOEXCEPT {
  *this = *this - d;
  return *this;
}

CONSTCD11 inline bool weekday::ok() const NOEXCEPT
{
  return wd_ <= 6;
}

CONSTCD11
inline
unsigned weekday::c_encoding() const NOEXCEPT
{
  return unsigned{wd_};
}

CONSTCD11
inline
unsigned weekday::iso_encoding() const NOEXCEPT
{
  return unsigned{((wd_ == 0u) ? 7u : wd_)};
}

CONSTCD11
inline
bool
operator==(const weekday &x, const weekday &y) NOEXCEPT {
  return x.wd_ == y.wd_;
}

CONSTCD11
inline
bool
operator!=(const weekday &x, const weekday &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD14
inline
days
operator-(const weekday &x, const weekday &y) NOEXCEPT {
  auto const wdu = x.wd_ - y.wd_;
  auto const wk = (wdu >= 0 ? wdu : wdu - 6) / 7;
  return days{wdu - wk * 7};
}

CONSTCD14
inline
weekday
operator+(const weekday &x, const days &y) NOEXCEPT {
  auto const wdu = static_cast<long long>(static_cast<unsigned>(x.wd_)) + y.count();
  auto const wk = (wdu >= 0 ? wdu : wdu - 6) / 7;
  return weekday{static_cast<unsigned>(wdu - wk * 7)};
}

CONSTCD14
inline
weekday
operator+(const days &x, const weekday &y) NOEXCEPT {
  return y + x;
}

CONSTCD14
inline
weekday
operator-(const weekday &x, const days &y) NOEXCEPT {
  return x + -y;
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday &wd)
{
  if (wd.ok()) {
    CharT fmt[] = {'%', 'a', 0};
    os << format(fmt, wd);
  }
  else {
    os << static_cast<unsigned>(wd.wd_) << " is not a valid weekday";
  }
  return os;
}

#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
inline namespace literals {

CONSTCD11
inline
date::day
operator "" _d(unsigned long long d) NOEXCEPT {
  return date::day{static_cast<unsigned>(d)};
}

CONSTCD11
inline
date::year
operator "" _y(unsigned long long y) NOEXCEPT {
  return date::year(static_cast<int>(y));
}
#endif  // !defined(_MSC_VER) || (_MSC_VER >= 1900)

CONSTDATA date::last_spec last{};

CONSTDATA date::month jan{1};
CONSTDATA date::month feb{2};
CONSTDATA date::month mar{3};
CONSTDATA date::month apr{4};
CONSTDATA date::month may{5};
CONSTDATA date::month jun{6};
CONSTDATA date::month jul{7};
CONSTDATA date::month aug{8};
CONSTDATA date::month sep{9};
CONSTDATA date::month oct{10};
CONSTDATA date::month nov{11};
CONSTDATA date::month dec{12};

CONSTDATA date::weekday sun{0u};
CONSTDATA date::weekday mon{1u};
CONSTDATA date::weekday tue{2u};
CONSTDATA date::weekday wed{3u};
CONSTDATA date::weekday thu{4u};
CONSTDATA date::weekday fri{5u};
CONSTDATA date::weekday sat{6u};

#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
}  // inline namespace literals
#endif

CONSTDATA date::month January{1};
CONSTDATA date::month February{2};
CONSTDATA date::month March{3};
CONSTDATA date::month April{4};
CONSTDATA date::month May{5};
CONSTDATA date::month June{6};
CONSTDATA date::month July{7};
CONSTDATA date::month August{8};
CONSTDATA date::month September{9};
CONSTDATA date::month October{10};
CONSTDATA date::month November{11};
CONSTDATA date::month December{12};

CONSTDATA date::weekday Monday{1};
CONSTDATA date::weekday Tuesday{2};
CONSTDATA date::weekday Wednesday{3};
CONSTDATA date::weekday Thursday{4};
CONSTDATA date::weekday Friday{5};
CONSTDATA date::weekday Saturday{6};
CONSTDATA date::weekday Sunday{7};

// weekday_indexed

CONSTCD11
inline
weekday
weekday_indexed::weekday() const NOEXCEPT
{
  return date::weekday{static_cast<unsigned>(wd_)};
}

CONSTCD11 inline unsigned weekday_indexed::index() const NOEXCEPT
{
  return index_;
}

CONSTCD11
inline
bool
weekday_indexed::ok() const NOEXCEPT
{
  return weekday().ok() && 1 <= index_ && index_ <= 5;
}

#ifdef __GNUC__
#  pragma GCC diagnostic push
#  pragma GCC diagnostic ignored "-Wconversion"
#endif  // __GNUC__

CONSTCD11
inline
weekday_indexed::weekday_indexed(const date::weekday &wd,
                                 unsigned index) NOEXCEPT
:
wd_(static_cast<decltype(wd_)>(static_cast<unsigned>(wd.wd_)))
, index_(static_cast<decltype(index_)>(index))
{}

#ifdef __GNUC__
#  pragma GCC diagnostic pop
#endif  // __GNUC__

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday_indexed &wdi)
{
  os << wdi.weekday() << '[' << wdi.index();
  if (!(1 <= wdi.index() && wdi.index() <= 5)) {
    os << " is not a valid index";
  }
  os << ']';
  return os;
}

CONSTCD11
inline
weekday_indexed
weekday::operator[](unsigned index) const NOEXCEPT
{
  return {*this, index};
}

CONSTCD11
inline
bool
operator==(const weekday_indexed &x, const weekday_indexed &y) NOEXCEPT {
  return x.weekday() == y.weekday() && x.index() == y.index();
}

CONSTCD11
inline
bool
operator!=(const weekday_indexed &x, const weekday_indexed &y) NOEXCEPT {
  return !(x == y);
}

// weekday_last

CONSTCD11 inline date::weekday weekday_last::weekday() const NOEXCEPT
{
  return wd_;
}
CONSTCD11 inline bool weekday_last::ok() const NOEXCEPT
{
  return wd_.ok();
}
CONSTCD11 inline weekday_last::weekday_last(const date::weekday &wd) NOEXCEPT :
wd_(wd) {}

CONSTCD11
inline
bool
operator==(const weekday_last &x, const weekday_last &y) NOEXCEPT {
  return x.weekday() == y.weekday();
}

CONSTCD11
inline
bool
operator!=(const weekday_last &x, const weekday_last &y) NOEXCEPT {
  return !(x == y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday_last &wdl)
{
  return os << wdl.weekday() << "[last]";
}

CONSTCD11
inline
weekday_last
weekday::operator[](last_spec) const NOEXCEPT
{
  return weekday_last{*this};
}

// year_month

CONSTCD11
inline
year_month::year_month(const date::year &y, const date::month &m) NOEXCEPT
:
y_(y)
, m_(m)
{}

CONSTCD11 inline year year_month::year() const NOEXCEPT
{
  return y_;
}
CONSTCD11 inline month year_month::month() const NOEXCEPT
{
  return m_;
}
CONSTCD11 inline bool year_month::ok() const NOEXCEPT
{
  return y_.ok() && m_.ok();
}

template<class>
CONSTCD14
inline
year_month &
year_month::operator+=(const months &dm) NOEXCEPT {
  *this = *this + dm;
  return *this;
}

template<class>
CONSTCD14
inline
year_month &
year_month::operator-=(const months &dm) NOEXCEPT {
  *this = *this - dm;
  return *this;
}

CONSTCD14
inline
year_month &
year_month::operator+=(const years &dy) NOEXCEPT {
  *this = *this + dy;
  return *this;
}

CONSTCD14
inline
year_month &
year_month::operator-=(const years &dy) NOEXCEPT {
  *this = *this - dy;
  return *this;
}

CONSTCD11
inline
bool
operator==(const year_month &x, const year_month &y) NOEXCEPT {
  return x.year() == y.year() && x.month() == y.month();
}

CONSTCD11
inline
bool
operator!=(const year_month &x, const year_month &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD11
inline
bool
operator<(const year_month &x, const year_month &y) NOEXCEPT {
  return x.year() < y.year() ? true
  : (x.year() > y.year() ? false
     : (x.month() < y.month()));
}

CONSTCD11
inline
bool
operator>(const year_month &x, const year_month &y) NOEXCEPT {
  return y < x;
}

CONSTCD11
inline
bool
operator<=(const year_month &x, const year_month &y) NOEXCEPT {
  return !(y < x);
}

CONSTCD11
inline
bool
operator>=(const year_month &x, const year_month &y) NOEXCEPT {
  return !(x < y);
}

template<class>
CONSTCD14
inline
year_month
operator+(const year_month &ym, const months &dm) NOEXCEPT {
  auto dmi = static_cast<int>(static_cast<unsigned>(ym.month())) - 1 + dm.count();
  auto dy = (dmi >= 0 ? dmi : dmi - 11) / 12;
  dmi = dmi - dy * 12 + 1;
  return (ym.year() + years(dy)) / month(static_cast<unsigned>(dmi));
}

template<class>
CONSTCD14
inline
year_month
operator+(const months &dm, const year_month &ym) NOEXCEPT {
  return ym + dm;
}

template<class>
CONSTCD14
inline
year_month
operator-(const year_month &ym, const months &dm) NOEXCEPT {
  return ym + -dm;
}

CONSTCD11
inline
months
operator-(const year_month &x, const year_month &y) NOEXCEPT {
  return (x.year() - y.year()) +
  months(static_cast<unsigned>(x.month()) - static_cast<unsigned>(y.month()));
}

CONSTCD11
inline
year_month
operator+(const year_month &ym, const years &dy) NOEXCEPT {
  return (ym.year() + dy) / ym.month();
}

CONSTCD11
inline
year_month
operator+(const years &dy, const year_month &ym) NOEXCEPT {
  return ym + dy;
}

CONSTCD11
inline
year_month
operator-(const year_month &ym, const years &dy) NOEXCEPT {
  return ym + -dy;
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month &ym)
{
  return os << ym.year() << '/' << ym.month();
}

// month_day

CONSTCD11
inline
month_day::month_day(const date::month &m, const date::day &d) NOEXCEPT
:
m_(m)
, d_(d)
{}

CONSTCD11 inline date::month month_day::month() const NOEXCEPT
{
  return m_;
}
CONSTCD11 inline date::day month_day::day() const NOEXCEPT
{
  return d_;
}

CONSTCD14
inline
bool
month_day::ok() const NOEXCEPT
{
  CONSTDATA date::day d[] = {
    date::day(31), date::day(29), date::day(31),
    date::day(30), date::day(31), date::day(30),
    date::day(31), date::day(31), date::day(30),
    date::day(31), date::day(30), date::day(31)
  };
  return m_.ok() && date::day{1} <= d_ &&d_ <= d[static_cast<unsigned>(m_) - 1];
}

CONSTCD11
inline
bool
operator==(const month_day &x, const month_day &y) NOEXCEPT {
  return x.month() == y.month() && x.day() == y.day();
}

CONSTCD11
inline
bool
operator!=(const month_day &x, const month_day &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD11
inline
bool
operator<(const month_day &x, const month_day &y) NOEXCEPT {
  return x.month() < y.month() ? true
  : (x.month() > y.month() ? false
     : (x.day() < y.day()));
}

CONSTCD11
inline
bool
operator>(const month_day &x, const month_day &y) NOEXCEPT {
  return y < x;
}

CONSTCD11
inline
bool
operator<=(const month_day &x, const month_day &y) NOEXCEPT {
  return !(y < x);
}

CONSTCD11
inline
bool
operator>=(const month_day &x, const month_day &y) NOEXCEPT {
  return !(x < y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_day &md)
{
  return os << md.month() << '/' << md.day();
}

// month_day_last

CONSTCD11 inline month month_day_last::month() const NOEXCEPT
{
  return m_;
}
CONSTCD11 inline bool month_day_last::ok() const NOEXCEPT
{
  return m_.ok();
}
CONSTCD11 inline month_day_last::month_day_last(const date::month &m) NOEXCEPT :
m_(m) {}

CONSTCD11
inline
bool
operator==(const month_day_last &x, const month_day_last &y) NOEXCEPT {
  return x.month() == y.month();
}

CONSTCD11
inline
bool
operator!=(const month_day_last &x, const month_day_last &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD11
inline
bool
operator<(const month_day_last &x, const month_day_last &y) NOEXCEPT {
  return x.month() < y.month();
}

CONSTCD11
inline
bool
operator>(const month_day_last &x, const month_day_last &y) NOEXCEPT {
  return y < x;
}

CONSTCD11
inline
bool
operator<=(const month_day_last &x, const month_day_last &y) NOEXCEPT {
  return !(y < x);
}

CONSTCD11
inline
bool
operator>=(const month_day_last &x, const month_day_last &y) NOEXCEPT {
  return !(x < y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_day_last &mdl)
{
  return os << mdl.month() << "/last";
}

// month_weekday

CONSTCD11
inline
month_weekday::month_weekday(const date::month &m,
                             const date::weekday_indexed &wdi) NOEXCEPT
:
m_(m)
, wdi_(wdi)
{}

CONSTCD11 inline month month_weekday::month() const NOEXCEPT
{
  return m_;
}

CONSTCD11
inline
weekday_indexed
month_weekday::weekday_indexed() const NOEXCEPT
{
  return wdi_;
}

CONSTCD11
inline
bool
month_weekday::ok() const NOEXCEPT
{
  return m_.ok() && wdi_.ok();
}

CONSTCD11
inline
bool
operator==(const month_weekday &x, const month_weekday &y) NOEXCEPT {
  return x.month() == y.month() && x.weekday_indexed() == y.weekday_indexed();
}

CONSTCD11
inline
bool
operator!=(const month_weekday &x, const month_weekday &y) NOEXCEPT {
  return !(x == y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_weekday &mwd)
{
  return os << mwd.month() << '/' << mwd.weekday_indexed();
}

// month_weekday_last

CONSTCD11
inline
month_weekday_last::month_weekday_last(const date::month &m,
                                       const date::weekday_last &wdl) NOEXCEPT
:
m_(m)
, wdl_(wdl)
{}

CONSTCD11 inline month month_weekday_last::month() const NOEXCEPT
{
  return m_;
}

CONSTCD11
inline
weekday_last
month_weekday_last::weekday_last() const NOEXCEPT
{
  return wdl_;
}

CONSTCD11
inline
bool
month_weekday_last::ok() const NOEXCEPT
{
  return m_.ok() && wdl_.ok();
}

CONSTCD11
inline
bool
operator==(const month_weekday_last &x, const month_weekday_last &y) NOEXCEPT {
  return x.month() == y.month() && x.weekday_last() == y.weekday_last();
}

CONSTCD11
inline
bool
operator!=(const month_weekday_last &x, const month_weekday_last &y) NOEXCEPT {
  return !(x == y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const month_weekday_last &mwdl)
{
  return os << mwdl.month() << '/' << mwdl.weekday_last();
}

// year_month_day_last

CONSTCD11
inline
year_month_day_last::year_month_day_last(const date::year &y,
    const date::month_day_last &mdl) NOEXCEPT
:
y_(y)
, mdl_(mdl)
{}

template<class>
CONSTCD14
inline
year_month_day_last &
year_month_day_last::operator+=(const months &m) NOEXCEPT {
  *this = *this + m;
  return *this;
}

template<class>
CONSTCD14
inline
year_month_day_last &
year_month_day_last::operator-=(const months &m) NOEXCEPT {
  *this = *this - m;
  return *this;
}

CONSTCD14
inline
year_month_day_last &
year_month_day_last::operator+=(const years &y) NOEXCEPT {
  *this = *this + y;
  return *this;
}

CONSTCD14
inline
year_month_day_last &
year_month_day_last::operator-=(const years &y) NOEXCEPT {
  *this = *this - y;
  return *this;
}

CONSTCD11 inline year year_month_day_last::year() const NOEXCEPT
{
  return y_;
}
CONSTCD11 inline month year_month_day_last::month() const NOEXCEPT
{
  return mdl_.month();
}

CONSTCD11
inline
month_day_last
year_month_day_last::month_day_last() const NOEXCEPT
{
  return mdl_;
}

CONSTCD14
inline
day
year_month_day_last::day() const NOEXCEPT
{
  CONSTDATA date::day d[] = {
    date::day(31), date::day(28), date::day(31),
    date::day(30), date::day(31), date::day(30),
    date::day(31), date::day(31), date::day(30),
    date::day(31), date::day(30), date::day(31)
  };
  return (month() != February || !y_.is_leap()) && mdl_.ok() ?
         d[static_cast<unsigned>(month()) - 1] : date::day{29};
}

CONSTCD14
inline
year_month_day_last::operator sys_days() const NOEXCEPT
{
  return sys_days(year() / month() / day());
}

CONSTCD14
inline
year_month_day_last::operator local_days() const NOEXCEPT
{
  return local_days(year() / month() / day());
}

CONSTCD11
inline
bool
year_month_day_last::ok() const NOEXCEPT
{
  return y_.ok() && mdl_.ok();
}

CONSTCD11
inline
bool
operator==(const year_month_day_last &x,
           const year_month_day_last &y) NOEXCEPT {
  return x.year() == y.year() && x.month_day_last() == y.month_day_last();
}

CONSTCD11
inline
bool
operator!=(const year_month_day_last &x,
           const year_month_day_last &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD11
inline
bool
operator<(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT {
  return x.year() < y.year() ? true
  : (x.year() > y.year() ? false
     : (x.month_day_last() < y.month_day_last()));
}

CONSTCD11
inline
bool
operator>(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT {
  return y < x;
}

CONSTCD11
inline
bool
operator<=(const year_month_day_last &x,
           const year_month_day_last &y) NOEXCEPT {
  return !(y < x);
}

CONSTCD11
inline
bool
operator>=(const year_month_day_last &x,
           const year_month_day_last &y) NOEXCEPT {
  return !(x < y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const year_month_day_last &ymdl)
{
  return os << ymdl.year() << '/' << ymdl.month_day_last();
}

template<class>
CONSTCD14
inline
year_month_day_last
operator+(const year_month_day_last &ymdl, const months &dm) NOEXCEPT {
  return (ymdl.year() / ymdl.month() + dm) / last;
}

template<class>
CONSTCD14
inline
year_month_day_last
operator+(const months &dm, const year_month_day_last &ymdl) NOEXCEPT {
  return ymdl + dm;
}

template<class>
CONSTCD14
inline
year_month_day_last
operator-(const year_month_day_last &ymdl, const months &dm) NOEXCEPT {
  return ymdl + (-dm);
}

CONSTCD11
inline
year_month_day_last
operator+(const year_month_day_last &ymdl, const years &dy) NOEXCEPT {
  return {ymdl.year() + dy, ymdl.month_day_last()};
}

CONSTCD11
inline
year_month_day_last
operator+(const years &dy, const year_month_day_last &ymdl) NOEXCEPT {
  return ymdl + dy;
}

CONSTCD11
inline
year_month_day_last
operator-(const year_month_day_last &ymdl, const years &dy) NOEXCEPT {
  return ymdl + (-dy);
}

// year_month_day

CONSTCD11
inline
year_month_day::year_month_day(const date::year &y, const date::month &m,
                               const date::day &d) NOEXCEPT
:
y_(y)
, m_(m)
, d_(d)
{}

CONSTCD14
inline
year_month_day::year_month_day(const year_month_day_last &ymdl) NOEXCEPT
:
y_(ymdl.year())
, m_(ymdl.month())
, d_(ymdl.day())
{}

CONSTCD14
inline
year_month_day::year_month_day(sys_days dp) NOEXCEPT
:
year_month_day(from_days(dp.time_since_epoch()))
{}

CONSTCD14
inline
year_month_day::year_month_day(local_days dp) NOEXCEPT
:
year_month_day(from_days(dp.time_since_epoch()))
{}

CONSTCD11 inline year year_month_day::year() const NOEXCEPT
{
  return y_;
}
CONSTCD11 inline month year_month_day::month() const NOEXCEPT
{
  return m_;
}
CONSTCD11 inline day year_month_day::day() const NOEXCEPT
{
  return d_;
}

template<class>
CONSTCD14
inline
year_month_day &
year_month_day::operator+=(const months &m) NOEXCEPT {
  *this = *this + m;
  return *this;
}

template<class>
CONSTCD14
inline
year_month_day &
year_month_day::operator-=(const months &m) NOEXCEPT {
  *this = *this - m;
  return *this;
}

CONSTCD14
inline
year_month_day &
year_month_day::operator+=(const years &y) NOEXCEPT {
  *this = *this + y;
  return *this;
}

CONSTCD14
inline
year_month_day &
year_month_day::operator-=(const years &y) NOEXCEPT {
  *this = *this - y;
  return *this;
}

CONSTCD14
inline
days
year_month_day::to_days() const NOEXCEPT
{
  static_assert(std::numeric_limits<unsigned>::digits >= 18,
                "This algorithm has not been ported to a 16 bit unsigned integer");
  static_assert(std::numeric_limits<int>::digits >= 20,
                "This algorithm has not been ported to a 16 bit signed integer");
  auto const y = static_cast<int>(y_) - (m_ <= February);
  auto const m = static_cast<unsigned>(m_);
  auto const d = static_cast<unsigned>(d_);
  auto const era = (y >= 0 ? y : y - 399) / 400;
  auto const yoe = static_cast<unsigned>(y - era * 400);       // [0, 399]
  auto const doy = (153 * (m > 2 ? m - 3 : m + 9) + 2) / 5 + d - 1; // [0, 365]
  auto const doe = yoe * 365 + yoe / 4 - yoe / 100 + doy;      // [0, 146096]
  return days{era * 146097 + static_cast<int>(doe) - 719468};
}

CONSTCD14
inline
year_month_day::operator sys_days() const NOEXCEPT
{
  return sys_days{to_days()};
}

CONSTCD14
inline
year_month_day::operator local_days() const NOEXCEPT
{
  return local_days{to_days()};
}

CONSTCD14
inline
bool
year_month_day::ok() const NOEXCEPT
{
  if (!(y_.ok() && m_.ok())) {
    return false;
  }
  return date::day{1} <= d_ &&d_ <= (y_ / m_ / last).day();
}

CONSTCD11
inline
bool
operator==(const year_month_day &x, const year_month_day &y) NOEXCEPT {
  return x.year() == y.year() && x.month() == y.month() && x.day() == y.day();
}

CONSTCD11
inline
bool
operator!=(const year_month_day &x, const year_month_day &y) NOEXCEPT {
  return !(x == y);
}

CONSTCD11
inline
bool
operator<(const year_month_day &x, const year_month_day &y) NOEXCEPT {
  return x.year() < y.year() ? true
  : (x.year() > y.year() ? false
     : (x.month() < y.month() ? true
        : (x.month() > y.month() ? false
           : (x.day() < y.day()))));
}

CONSTCD11
inline
bool
operator>(const year_month_day &x, const year_month_day &y) NOEXCEPT {
  return y < x;
}

CONSTCD11
inline
bool
operator<=(const year_month_day &x, const year_month_day &y) NOEXCEPT {
  return !(y < x);
}

CONSTCD11
inline
bool
operator>=(const year_month_day &x, const year_month_day &y) NOEXCEPT {
  return !(x < y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_day &ymd)
{
  detail::save_ostream<CharT, Traits> _(os);
  os.fill('0');
  os.flags(std::ios::dec | std::ios::right);
  os << ymd.year() << '-';
  os.width(2);
  os << static_cast<unsigned>(ymd.month()) << '-';
  os << ymd.day();
  if (!ymd.ok()) {
    os << " is not a valid date";
  }
  return os;
}

CONSTCD14
inline
year_month_day
year_month_day::from_days(days dp) NOEXCEPT {
  static_assert(std::numeric_limits<unsigned>::digits >= 18,
                "This algorithm has not been ported to a 16 bit unsigned integer");
  static_assert(std::numeric_limits<int>::digits >= 20,
                "This algorithm has not been ported to a 16 bit signed integer");
  auto const z = dp.count() + 719468;
  auto const era = (z >= 0 ? z : z - 146096) / 146097;
  auto const doe = static_cast<unsigned>(z - era * 146097);          // [0, 146096]
  auto const yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365; // [0, 399]
  auto const y = static_cast<days::rep>(yoe) + era * 400;
  auto const doy = doe - (365 * yoe + yoe / 4 - yoe / 100);          // [0, 365]
  auto const mp = (5 * doy + 2) / 153;                               // [0, 11]
  auto const d = doy - (153 * mp + 2) / 5 + 1;                       // [1, 31]
  auto const m = mp < 10 ? mp + 3 : mp - 9;                          // [1, 12]
  return year_month_day{date::year{y + (m <= 2)}, date::month(m), date::day(d)};
}

template<class>
CONSTCD14
inline
year_month_day
operator+(const year_month_day &ymd, const months &dm) NOEXCEPT {
  return (ymd.year() / ymd.month() + dm) / ymd.day();
}

template<class>
CONSTCD14
inline
year_month_day
operator+(const months &dm, const year_month_day &ymd) NOEXCEPT {
  return ymd + dm;
}

template<class>
CONSTCD14
inline
year_month_day
operator-(const year_month_day &ymd, const months &dm) NOEXCEPT {
  return ymd + (-dm);
}

CONSTCD11
inline
year_month_day
operator+(const year_month_day &ymd, const years &dy) NOEXCEPT {
  return (ymd.year() + dy) / ymd.month() / ymd.day();
}

CONSTCD11
inline
year_month_day
operator+(const years &dy, const year_month_day &ymd) NOEXCEPT {
  return ymd + dy;
}

CONSTCD11
inline
year_month_day
operator-(const year_month_day &ymd, const years &dy) NOEXCEPT {
  return ymd + (-dy);
}

// year_month_weekday

CONSTCD11
inline
year_month_weekday::year_month_weekday(const date::year &y,
                                       const date::month &m,
                                       const date::weekday_indexed &wdi)
NOEXCEPT
:
y_(y)
, m_(m)
, wdi_(wdi)
{}

CONSTCD14
inline
year_month_weekday::year_month_weekday(const sys_days &dp) NOEXCEPT
:
year_month_weekday(from_days(dp.time_since_epoch()))
{}

CONSTCD14
inline
year_month_weekday::year_month_weekday(const local_days &dp) NOEXCEPT
:
year_month_weekday(from_days(dp.time_since_epoch()))
{}

template<class>
CONSTCD14
inline
year_month_weekday &
year_month_weekday::operator+=(const months &m) NOEXCEPT {
  *this = *this + m;
  return *this;
}

template<class>
CONSTCD14
inline
year_month_weekday &
year_month_weekday::operator-=(const months &m) NOEXCEPT {
  *this = *this - m;
  return *this;
}

CONSTCD14
inline
year_month_weekday &
year_month_weekday::operator+=(const years &y) NOEXCEPT {
  *this = *this + y;
  return *this;
}

CONSTCD14
inline
year_month_weekday &
year_month_weekday::operator-=(const years &y) NOEXCEPT {
  *this = *this - y;
  return *this;
}

CONSTCD11 inline year year_month_weekday::year() const NOEXCEPT
{
  return y_;
}
CONSTCD11 inline month year_month_weekday::month() const NOEXCEPT
{
  return m_;
}

CONSTCD11
inline
weekday
year_month_weekday::weekday() const NOEXCEPT
{
  return wdi_.weekday();
}

CONSTCD11
inline
unsigned
year_month_weekday::index() const NOEXCEPT
{
  return wdi_.index();
}

CONSTCD11
inline
weekday_indexed
year_month_weekday::weekday_indexed() const NOEXCEPT
{
  return wdi_;
}

CONSTCD14
inline
year_month_weekday::operator sys_days() const NOEXCEPT
{
  return sys_days{to_days()};
}

CONSTCD14
inline
year_month_weekday::operator local_days() const NOEXCEPT
{
  return local_days{to_days()};
}

CONSTCD14
inline
bool
year_month_weekday::ok() const NOEXCEPT
{
  if (!y_.ok() || !m_.ok() || !wdi_.weekday().ok() || wdi_.index() < 1) {
    return false;
  }
  if (wdi_.index() <= 4) {
    return true;
  }
  auto d2 = wdi_.weekday() - date::weekday(static_cast<sys_days>(y_ / m_ / 1)) +
            days((wdi_.index() - 1) * 7 + 1);
  return static_cast<unsigned>(d2.count()) <= static_cast<unsigned>((
           y_ / m_ / last).day());
}

CONSTCD14
inline
year_month_weekday
year_month_weekday::from_days(days d) NOEXCEPT {
  sys_days dp{d};
  auto const wd = date::weekday(dp);
  auto const ymd = year_month_day(dp);
  return {ymd.year(), ymd.month(), wd[(static_cast<unsigned>(ymd.day()) - 1) / 7 + 1]};
}

CONSTCD14
inline
days
year_month_weekday::to_days() const NOEXCEPT
{
  auto d = sys_days(y_ / m_ / 1);
  return (d + (wdi_.weekday() - date::weekday(d) + days{(wdi_.index() - 1) * 7})
         ).time_since_epoch();
}

CONSTCD11
inline
bool
operator==(const year_month_weekday &x, const year_month_weekday &y) NOEXCEPT {
  return x.year() == y.year() && x.month() == y.month() &&
  x.weekday_indexed() == y.weekday_indexed();
}

CONSTCD11
inline
bool
operator!=(const year_month_weekday &x, const year_month_weekday &y) NOEXCEPT {
  return !(x == y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const year_month_weekday &ymwdi)
{
  return os << ymwdi.year() << '/' << ymwdi.month()
         << '/' << ymwdi.weekday_indexed();
}

template<class>
CONSTCD14
inline
year_month_weekday
operator+(const year_month_weekday &ymwd, const months &dm) NOEXCEPT {
  return (ymwd.year() / ymwd.month() + dm) / ymwd.weekday_indexed();
}

template<class>
CONSTCD14
inline
year_month_weekday
operator+(const months &dm, const year_month_weekday &ymwd) NOEXCEPT {
  return ymwd + dm;
}

template<class>
CONSTCD14
inline
year_month_weekday
operator-(const year_month_weekday &ymwd, const months &dm) NOEXCEPT {
  return ymwd + (-dm);
}

CONSTCD11
inline
year_month_weekday
operator+(const year_month_weekday &ymwd, const years &dy) NOEXCEPT {
  return {ymwd.year() + dy, ymwd.month(), ymwd.weekday_indexed()};
}

CONSTCD11
inline
year_month_weekday
operator+(const years &dy, const year_month_weekday &ymwd) NOEXCEPT {
  return ymwd + dy;
}

CONSTCD11
inline
year_month_weekday
operator-(const year_month_weekday &ymwd, const years &dy) NOEXCEPT {
  return ymwd + (-dy);
}

// year_month_weekday_last

CONSTCD11
inline
year_month_weekday_last::year_month_weekday_last(const date::year &y,
    const date::month &m,
    const date::weekday_last &wdl) NOEXCEPT
:
y_(y)
, m_(m)
, wdl_(wdl)
{}

template<class>
CONSTCD14
inline
year_month_weekday_last &
year_month_weekday_last::operator+=(const months &m) NOEXCEPT {
  *this = *this + m;
  return *this;
}

template<class>
CONSTCD14
inline
year_month_weekday_last &
year_month_weekday_last::operator-=(const months &m) NOEXCEPT {
  *this = *this - m;
  return *this;
}

CONSTCD14
inline
year_month_weekday_last &
year_month_weekday_last::operator+=(const years &y) NOEXCEPT {
  *this = *this + y;
  return *this;
}

CONSTCD14
inline
year_month_weekday_last &
year_month_weekday_last::operator-=(const years &y) NOEXCEPT {
  *this = *this - y;
  return *this;
}

CONSTCD11 inline year year_month_weekday_last::year() const NOEXCEPT
{
  return y_;
}
CONSTCD11 inline month year_month_weekday_last::month() const NOEXCEPT
{
  return m_;
}

CONSTCD11
inline
weekday
year_month_weekday_last::weekday() const NOEXCEPT
{
  return wdl_.weekday();
}

CONSTCD11
inline
weekday_last
year_month_weekday_last::weekday_last() const NOEXCEPT
{
  return wdl_;
}

CONSTCD14
inline
year_month_weekday_last::operator sys_days() const NOEXCEPT
{
  return sys_days{to_days()};
}

CONSTCD14
inline
year_month_weekday_last::operator local_days() const NOEXCEPT
{
  return local_days{to_days()};
}

CONSTCD11
inline
bool
year_month_weekday_last::ok() const NOEXCEPT
{
  return y_.ok() && m_.ok() && wdl_.ok();
}

CONSTCD14
inline
days
year_month_weekday_last::to_days() const NOEXCEPT
{
  auto const d = sys_days(y_ / m_ / last);
  return (d - (date::weekday{d} - wdl_.weekday())).time_since_epoch();
}

CONSTCD11
inline
bool
operator==(const year_month_weekday_last &x,
           const year_month_weekday_last &y) NOEXCEPT {
  return x.year() == y.year() && x.month() == y.month() &&
  x.weekday_last() == y.weekday_last();
}

CONSTCD11
inline
bool
operator!=(const year_month_weekday_last &x,
           const year_month_weekday_last &y) NOEXCEPT {
  return !(x == y);
}

template<class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const year_month_weekday_last &ymwdl)
{
  return os << ymwdl.year() << '/' << ymwdl.month() << '/' <<
         ymwdl.weekday_last();
}

template<class>
CONSTCD14
inline
year_month_weekday_last
operator+(const year_month_weekday_last &ymwdl, const months &dm) NOEXCEPT {
  return (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_last();
}

template<class>
CONSTCD14
inline
year_month_weekday_last
operator+(const months &dm, const year_month_weekday_last &ymwdl) NOEXCEPT {
  return ymwdl + dm;
}

template<class>
CONSTCD14
inline
year_month_weekday_last
operator-(const year_month_weekday_last &ymwdl, const months &dm) NOEXCEPT {
  return ymwdl + (-dm);
}

CONSTCD11
inline
year_month_weekday_last
operator+(const year_month_weekday_last &ymwdl, const years &dy) NOEXCEPT {
  return {ymwdl.year() + dy, ymwdl.month(), ymwdl.weekday_last()};
}

CONSTCD11
inline
year_month_weekday_last
operator+(const years &dy, const year_month_weekday_last &ymwdl) NOEXCEPT {
  return ymwdl + dy;
}

CONSTCD11
inline
year_month_weekday_last
operator-(const year_month_weekday_last &ymwdl, const years &dy) NOEXCEPT {
  return ymwdl + (-dy);
}

// year_month from operator/()

CONSTCD11
inline
year_month
operator/(const year &y, const month &m) NOEXCEPT {
  return {y, m};
}

CONSTCD11
inline
year_month
operator/(const year &y, int   m) NOEXCEPT {
  return y / month(static_cast<unsigned>(m));
}

// month_day from operator/()

CONSTCD11
inline
month_day
operator/(const month &m, const day &d) NOEXCEPT {
  return {m, d};
}

CONSTCD11
inline
month_day
operator/(const day &d, const month &m) NOEXCEPT {
  return m / d;
}

CONSTCD11
inline
month_day
operator/(const month &m, int d) NOEXCEPT {
  return m / day(static_cast<unsigned>(d));
}

CONSTCD11
inline
month_day
operator/(int m, const day &d) NOEXCEPT {
  return month(static_cast<unsigned>(m)) / d;
}

CONSTCD11 inline month_day operator/(const day &d, int m) NOEXCEPT {return m / d;}

// month_day_last from operator/()

CONSTCD11
inline
month_day_last
operator/(const month &m, last_spec) NOEXCEPT {
  return month_day_last{m};
}

CONSTCD11
inline
month_day_last
operator/(last_spec, const month &m) NOEXCEPT {
  return m / last;
}

CONSTCD11
inline
month_day_last
operator/(int m, last_spec) NOEXCEPT {
  return month(static_cast<unsigned>(m)) / last;
}

CONSTCD11
inline
month_day_last
operator/(last_spec, int m) NOEXCEPT {
  return m / last;
}

// month_weekday from operator/()

CONSTCD11
inline
month_weekday
operator/(const month &m, const weekday_indexed &wdi) NOEXCEPT {
  return {m, wdi};
}

CONSTCD11
inline
month_weekday
operator/(const weekday_indexed &wdi, const month &m) NOEXCEPT {
  return m / wdi;
}

CONSTCD11
inline
month_weekday
operator/(int m, const weekday_indexed &wdi) NOEXCEPT {
  return month(static_cast<unsigned>(m)) / wdi;
}

CONSTCD11
inline
month_weekday
operator/(const weekday_indexed &wdi, int m) NOEXCEPT {
  return m / wdi;
}

// month_weekday_last from operator/()

CONSTCD11
inline
month_weekday_last
operator/(const month &m, const weekday_last &wdl) NOEXCEPT {
  return {m, wdl};
}

CONSTCD11
inline
month_weekday_last
operator/(const weekday_last &wdl, const month &m) NOEXCEPT {
  return m / wdl;
}

CONSTCD11
inline
month_weekday_last
operator/(int m, const weekday_last &wdl) NOEXCEPT {
  return month(static_cast<unsigned>(m)) / wdl;
}

CONSTCD11
inline
month_weekday_last
operator/(const weekday_last &wdl, int m) NOEXCEPT {
  return m / wdl;
}

// year_month_day from operator/()

CONSTCD11
inline
year_month_day
operator/(const year_month &ym, const day &d) NOEXCEPT {
  return {ym.year(), ym.month(), d};
}

CONSTCD11
inline
year_month_day
operator/(const year_month &ym, int d)  NOEXCEPT {
  return ym / day(static_cast<unsigned>(d));
}

CONSTCD11
inline
year_month_day
operator/(const year &y, const month_day &md) NOEXCEPT {
  return y / md.month() / md.day();
}

CONSTCD11
inline
year_month_day
operator/(int y, const month_day &md) NOEXCEPT {
  return year(y) / md;
}

CONSTCD11
inline
year_month_day
operator/(const month_day &md, const year &y)  NOEXCEPT {
  return y / md;
}

CONSTCD11
inline
year_month_day
operator/(const month_day &md, int y) NOEXCEPT {
  return year(y) / md;
}

// year_month_day_last from operator/()

CONSTCD11
inline
year_month_day_last
operator/(const year_month &ym, last_spec) NOEXCEPT {
  return {ym.year(), month_day_last{ym.month()}};
}

CONSTCD11
inline
year_month_day_last
operator/(const year &y, const month_day_last &mdl) NOEXCEPT {
  return {y, mdl};
}

CONSTCD11
inline
year_month_day_last
operator/(int y, const month_day_last &mdl) NOEXCEPT {
  return year(y) / mdl;
}

CONSTCD11
inline
year_month_day_last
operator/(const month_day_last &mdl, const year &y) NOEXCEPT {
  return y / mdl;
}

CONSTCD11
inline
year_month_day_last
operator/(const month_day_last &mdl, int y) NOEXCEPT {
  return year(y) / mdl;
}

// year_month_weekday from operator/()

CONSTCD11
inline
year_month_weekday
operator/(const year_month &ym, const weekday_indexed &wdi) NOEXCEPT {
  return {ym.year(), ym.month(), wdi};
}

CONSTCD11
inline
year_month_weekday
operator/(const year &y, const month_weekday &mwd) NOEXCEPT {
  return {y, mwd.month(), mwd.weekday_indexed()};
}

CONSTCD11
inline
year_month_weekday
operator/(int y, const month_weekday &mwd) NOEXCEPT {
  return year(y) / mwd;
}

CONSTCD11
inline
year_month_weekday
operator/(const month_weekday &mwd, const year &y) NOEXCEPT {
  return y / mwd;
}

CONSTCD11
inline
year_month_weekday
operator/(const month_weekday &mwd, int y) NOEXCEPT {
  return year(y) / mwd;
}

// year_month_weekday_last from operator/()

CONSTCD11
inline
year_month_weekday_last
operator/(const year_month &ym, const weekday_last &wdl) NOEXCEPT {
  return {ym.year(), ym.month(), wdl};
}

CONSTCD11
inline
year_month_weekday_last
operator/(const year &y, const month_weekday_last &mwdl) NOEXCEPT {
  return {y, mwdl.month(), mwdl.weekday_last()};
}

CONSTCD11
inline
year_month_weekday_last
operator/(int y, const month_weekday_last &mwdl) NOEXCEPT {
  return year(y) / mwdl;
}

CONSTCD11
inline
year_month_weekday_last
operator/(const month_weekday_last &mwdl, const year &y) NOEXCEPT {
  return y / mwdl;
}

CONSTCD11
inline
year_month_weekday_last
operator/(const month_weekday_last &mwdl, int y) NOEXCEPT {
  return year(y) / mwdl;
}

template <class Duration>
struct fields;

template <class CharT, class Traits, class Duration>
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const fields<Duration> &fds, const std::string *abbrev = nullptr,
          const std::chrono::seconds *offset_sec = nullptr);

template <class CharT, class Traits, class Duration, class Alloc>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            fields<Duration> &fds, std::basic_string<CharT, Traits, Alloc> *abbrev =
              nullptr,
            std::chrono::minutes *offset = nullptr);

// hh_mm_ss

namespace detail {

struct undocumented {
  explicit undocumented() = default;
};

// width<n>::value is the number of fractional decimal digits in 1/n
// width<0>::value and width<1>::value are defined to be 0
// If 1/n takes more than 18 fractional decimal digits,
//   the result is truncated to 19.
// Example:  width<2>::value    ==  1
// Example:  width<3>::value    == 19
// Example:  width<4>::value    ==  2
// Example:  width<10>::value   ==  1
// Example:  width<1000>::value ==  3
template < std::uint64_t n, std::uint64_t d = 10, unsigned w = 0,
           bool should_continue = !(n < 2) && d != 0 && (w < 19) >
struct width {
  static CONSTDATA unsigned value = 1 + width < n, d % n * 10, w + 1 >::value;
};

template <std::uint64_t n, std::uint64_t d, unsigned w>
struct width<n, d, w, false> {
  static CONSTDATA unsigned value = 0;
};

template <unsigned exp>
struct static_pow10 {
private:
  static CONSTDATA std::uint64_t h = static_pow10 < exp / 2 >::value;
public:
  static CONSTDATA std::uint64_t value = h * h * (exp % 2 ? 10 : 1);
};

template <>
struct static_pow10<0> {
  static CONSTDATA std::uint64_t value = 1;
};

template <class Duration>
class decimal_format_seconds {
  using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
  using rep = typename CT::rep;
public:
  static unsigned constexpr width = detail::width<CT::period::den>::value < 19 ?
                                    detail::width<CT::period::den>::value : 6u;
  using precision = std::chrono::duration<rep,
        std::ratio<1, static_pow10<width>::value>>;

private:
  std::chrono::seconds s_;
  precision            sub_s_;

public:
  CONSTCD11 decimal_format_seconds()
    : s_()
    , sub_s_()
  {}

  CONSTCD11 explicit decimal_format_seconds(const Duration &d) NOEXCEPT
:
  s_(std::chrono::duration_cast<std::chrono::seconds>(d))
  , sub_s_(std::chrono::treat_as_floating_point<rep>::value ? d - s_ :
           std::chrono::duration_cast<precision>(d - s_))
  {}

  CONSTCD14 std::chrono::seconds &seconds() NOEXCEPT {return s_;}
  CONSTCD11 std::chrono::seconds seconds() const NOEXCEPT
  {
    return s_;
  }
  CONSTCD11 precision subseconds() const NOEXCEPT
  {
    return sub_s_;
  }

  CONSTCD14 precision to_duration() const NOEXCEPT
  {
    return s_ + sub_s_;
  }

  CONSTCD11 bool in_conventional_range() const NOEXCEPT
  {
    return sub_s_ < std::chrono::seconds{1} &&s_ < std::chrono::minutes{1};
  }

  template <class CharT, class Traits>
  friend
  std::basic_ostream<CharT, Traits> &
  operator<<(std::basic_ostream<CharT, Traits> &os,
             const decimal_format_seconds &x)
  {
    return x.print(os, std::chrono::treat_as_floating_point<rep> {});
  }

  template <class CharT, class Traits>
  std::basic_ostream<CharT, Traits> &
  print(std::basic_ostream<CharT, Traits> &os, std::true_type) const
  {
    date::detail::save_ostream<CharT, Traits> _(os);
    std::chrono::duration<rep> d = s_ + sub_s_;
    if (d < std::chrono::seconds{10})
      os << '0';
    os << std::fixed << d.count();
    return os;
  }

  template <class CharT, class Traits>
  std::basic_ostream<CharT, Traits> &
  print(std::basic_ostream<CharT, Traits> &os, std::false_type) const
  {
    date::detail::save_ostream<CharT, Traits> _(os);
    os.fill('0');
    os.flags(std::ios::dec | std::ios::right);
    os.width(2);
    os << s_.count();
    if (width > 0) {
#if !ONLY_C_LOCALE
      os << std::use_facet<std::numpunct<CharT>>(os.getloc()).decimal_point();
#else
      os << '.';
#endif
      os.width(width);
      os << sub_s_.count();
    }
    return os;
  }
};

template <class Rep, class Period>
inline
CONSTCD11
typename std::enable_if
<
  std::numeric_limits<Rep>::is_signed,
  std::chrono::duration<Rep, Period>
  >::type
abs(std::chrono::duration<Rep, Period> d)
{
  return d >= d.zero() ? +d : -d;
}

template <class Rep, class Period>
inline
CONSTCD11
typename std::enable_if
<
  !std::numeric_limits<Rep>::is_signed,
  std::chrono::duration<Rep, Period>
  >::type
abs(std::chrono::duration<Rep, Period> d)
{
  return d;
}

}  // namespace detail

template <class Duration>
class hh_mm_ss {
  using dfs = detail::decimal_format_seconds<typename std::common_type<Duration,
      std::chrono::seconds>::type>;

  std::chrono::hours h_;
  std::chrono::minutes m_;
  dfs s_;
  bool neg_;

public:
  static unsigned CONSTDATA fractional_width = dfs::width;
  using precision = typename dfs::precision;

  CONSTCD11 hh_mm_ss() NOEXCEPT
:
  hh_mm_ss(Duration::zero())
  {}

  CONSTCD11 explicit hh_mm_ss(Duration d) NOEXCEPT
:
  h_(std::chrono::duration_cast<std::chrono::hours>(detail::abs(d)))
  , m_(std::chrono::duration_cast<std::chrono::minutes>(detail::abs(d)) - h_)
  , s_(detail::abs(d) - h_ - m_)
  , neg_(d < Duration::zero())
  {}

  CONSTCD11 std::chrono::hours hours() const NOEXCEPT
  {
    return h_;
  }
  CONSTCD11 std::chrono::minutes minutes() const NOEXCEPT
  {
    return m_;
  }
  CONSTCD11 std::chrono::seconds seconds() const NOEXCEPT
  {
    return s_.seconds();
  }
  CONSTCD14 std::chrono::seconds &
  seconds(detail::undocumented) NOEXCEPT {return s_.seconds();}
  CONSTCD11 precision subseconds() const NOEXCEPT
  {
    return s_.subseconds();
  }
  CONSTCD11 bool is_negative() const NOEXCEPT
  {
    return neg_;
  }

  CONSTCD11 explicit operator  precision()   const NOEXCEPT
  {
    return to_duration();
  }
  CONSTCD11          precision to_duration() const NOEXCEPT
  {
    return (h_ + m_ + s_.to_duration()) * (1 - 2 * neg_);
  }

  CONSTCD11 bool in_conventional_range() const NOEXCEPT
  {
    return !neg_ && h_ < days{1} &&m_ < std::chrono::hours{1} &&
           s_.in_conventional_range();
  }

private:

  template <class charT, class traits>
  friend
  std::basic_ostream<charT, traits> &
  operator<<(std::basic_ostream<charT, traits> &os, hh_mm_ss const &tod)
  {
    if (tod.is_negative()) {
      os << '-';
    }
    if (tod.h_ < std::chrono::hours{10})
      os << '0';
    os << tod.h_.count() << ':';
    if (tod.m_ < std::chrono::minutes{10})
      os << '0';
    os << tod.m_.count() << ':' << tod.s_;
    return os;
  }

  template <class CharT, class Traits, class Duration2>
  friend
  std::basic_ostream<CharT, Traits> &
  date::to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
                  const fields<Duration2> &fds, const std::string *abbrev,
                  const std::chrono::seconds *offset_sec);

  template <class CharT, class Traits, class Duration2, class Alloc>
  friend
  std::basic_istream<CharT, Traits> &
  date::from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
                    fields<Duration2> &fds,
                    std::basic_string<CharT, Traits, Alloc> *abbrev, std::chrono::minutes *offset);
};

inline
CONSTCD14
bool
is_am(std::chrono::hours const &h) NOEXCEPT {
  using std::chrono::hours;
  return hours{0} <= h &&h < hours{12};
}

inline
CONSTCD14
bool
is_pm(std::chrono::hours const &h) NOEXCEPT {
  using std::chrono::hours;
  return hours{12} <= h &&h < hours{24};
}

inline
CONSTCD14
std::chrono::hours
make12(std::chrono::hours h) NOEXCEPT {
  using std::chrono::hours;
  if (h < hours{12})
  {
    if (h == hours{0})
    h = hours{12};
  }
  else
  {
    if (h != hours{12})
      h -= hours{12};
  }
  return h;
}

inline
CONSTCD14
std::chrono::hours
make24(std::chrono::hours h, bool is_pm) NOEXCEPT {
  using std::chrono::hours;
  if (is_pm)
  {
    if (h != hours{12})
    h += hours{12};
  }
  else if (h == hours{12})
    h = hours{0};
  return h;
}

template <class Duration>
using time_of_day = hh_mm_ss<Duration>;

template < class Rep, class Period,
           class = typename std::enable_if
           < !std::chrono::treat_as_floating_point<Rep>::value >::type >
CONSTCD11
inline
hh_mm_ss<std::chrono::duration<Rep, Period>>
make_time(const std::chrono::duration<Rep, Period> &d)
{
  return hh_mm_ss<std::chrono::duration<Rep, Period>>(d);
}

template <class CharT, class Traits, class Duration>
inline
typename std::enable_if
<
  !std::chrono::treat_as_floating_point<typename Duration::rep>::value &&
  std::ratio_less<typename Duration::period, days::period>::value
  , std::basic_ostream<CharT, Traits> &
  >::type
operator<<(std::basic_ostream<CharT, Traits> &os, const sys_time<Duration> &tp)
{
  auto const dp = date::floor<days>(tp);
  return os << year_month_day(dp) << ' ' << make_time(tp - dp);
}

template <class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const sys_days &dp)
{
  return os << year_month_day(dp);
}

template <class CharT, class Traits, class Duration>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const local_time<Duration> &ut)
{
  return (os << sys_time<Duration> {ut.time_since_epoch()});
}

namespace detail {

template <class CharT, std::size_t N>
class string_literal;

template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
inline
CONSTCD14
string_literal < typename std::conditional < sizeof(CharT2) <= sizeof(CharT1),
                 CharT1, CharT2 >::type,
                 N1 + N2 - 1 >
                 operator+(const string_literal<CharT1, N1> &x,
                           const string_literal<CharT2, N2> &y) NOEXCEPT;

template <class CharT, std::size_t N>
class string_literal {
  CharT p_[N];

  CONSTCD11 string_literal() NOEXCEPT
:
  p_{}
  {}

public:
  using const_iterator = const CharT*;

  string_literal(string_literal const &) = default;
  string_literal &operator=(string_literal const &) = delete;

  template <std::size_t N1 = 2,
            class = typename std::enable_if<N1 == N>::type>
  CONSTCD11 string_literal(CharT c) NOEXCEPT
:
  p_{c} {
  }

  template <std::size_t N1 = 3,
            class = typename std::enable_if<N1 == N>::type>
  CONSTCD11 string_literal(CharT c1, CharT c2) NOEXCEPT
:
  p_{c1, c2} {
  }

  template <std::size_t N1 = 4,
            class = typename std::enable_if<N1 == N>::type>
  CONSTCD11 string_literal(CharT c1, CharT c2, CharT c3) NOEXCEPT
:
  p_{c1, c2, c3} {
  }

  CONSTCD14 string_literal(const CharT(&a)[N]) NOEXCEPT
:
  p_{} {
    for (std::size_t i = 0; i < N; ++i)
    {
      p_[i] = a[i];
    }
  }

  template < class U = CharT,
             class = typename std::enable_if<(1 < sizeof(U))>::type>
             CONSTCD14 string_literal(const char(&a)[N]) NOEXCEPT
           : p_ {}
  {
    for (std::size_t i = 0; i < N; ++i) {
      p_[i] = a[i];
    }
  }

  template < class CharT2,
             class = typename std::enable_if < !std::is_same<CharT2, CharT>::value >::type >
  CONSTCD14 string_literal(string_literal<CharT2, N> const &a) NOEXCEPT
: p_ {}
  {
    for (std::size_t i = 0; i < N; ++i) {
      p_[i] = a[i];
    }
  }

  CONSTCD11 const CharT *data() const NOEXCEPT
  {
    return p_;
  }
  CONSTCD11 std::size_t size() const NOEXCEPT
  {
    return N - 1;
  }

  CONSTCD11 const_iterator begin() const NOEXCEPT
  {
    return p_;
  }
  CONSTCD11 const_iterator end()   const NOEXCEPT
  {
    return p_ + N - 1;
  }

  CONSTCD11 CharT const &operator[](std::size_t n) const NOEXCEPT
  {
    return p_[n];
  }

  template <class Traits>
  friend
  std::basic_ostream<CharT, Traits> &
  operator<<(std::basic_ostream<CharT, Traits> &os, const string_literal &s)
  {
    return os << s.p_;
  }

  template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
  friend
  CONSTCD14
  string_literal < typename std::conditional < sizeof(CharT2) <= sizeof(CharT1),
                   CharT1, CharT2 >::type,
                   N1 + N2 - 1 >
                   operator+(const string_literal<CharT1, N1> &x,
                             const string_literal<CharT2, N2> &y) NOEXCEPT;
};

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 3>
operator+(const string_literal<CharT, 2> &x,
          const string_literal<CharT, 2> &y) NOEXCEPT {
  return string_literal<CharT, 3>(x[0], y[0]);
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 4>
operator+(const string_literal<CharT, 3> &x,
          const string_literal<CharT, 2> &y) NOEXCEPT {
  return string_literal<CharT, 4>(x[0], x[1], y[0]);
}

template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
CONSTCD14
inline
string_literal < typename std::conditional < sizeof(CharT2) <= sizeof(CharT1),
                 CharT1, CharT2 >::type,
                 N1 + N2 - 1 >
                 operator+(const string_literal<CharT1, N1> &x,
const string_literal<CharT2, N2> &y) NOEXCEPT {
  using CT = typename std::conditional < sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2 >::type;

  string_literal < CT, N1 + N2 - 1 > r;
  std::size_t i = 0;
  for (; i < N1 - 1; ++i)
  {
    r.p_[i] = CT(x.p_[i]);
  }
  for (std::size_t j = 0; j < N2; ++j, ++i)
  {
    r.p_[i] = CT(y.p_[j]);
  }

  return r;
}


template <class CharT, class Traits, class Alloc, std::size_t N>
inline
std::basic_string<CharT, Traits, Alloc>
operator+(std::basic_string<CharT, Traits, Alloc> x,
          const string_literal<CharT, N> &y)
{
  x.append(y.data(), y.size());
  return x;
}

#if __cplusplus >= 201402  && (!defined(__EDG_VERSION__) || __EDG_VERSION__ > 411) \
                           && (!defined(__SUNPRO_CC) || __SUNPRO_CC > 0x5150)

template < class CharT,
class = std::enable_if_t < std::is_same<CharT, char> {} ||
std::is_same<CharT, wchar_t> {} ||
std::is_same<CharT, char16_t> {} ||
std::is_same<CharT, char32_t> {} >>
                                 CONSTCD14
                                 inline
                                 string_literal<CharT, 2>
msl(CharT c) NOEXCEPT {
  return string_literal<CharT, 2>{c};
}

CONSTCD14
inline
std::size_t
to_string_len(std::intmax_t i)
{
  std::size_t r = 0;
  do {
    i /= 10;
    ++r;
  }
  while (i > 0);
  return r;
}

template <std::intmax_t N>
CONSTCD14
inline
std::enable_if_t
<
  N < 10,
      string_literal < char, to_string_len(N) + 1 >
      >
msl() NOEXCEPT {
  return msl(char(N % 10 + '0'));
}

template <std::intmax_t N>
CONSTCD14
inline
std::enable_if_t
<
  10 <= N,
      string_literal < char, to_string_len(N) + 1 >
      >
msl() NOEXCEPT {
  return msl < N / 10 > () + msl(char(N % 10 + '0'));
}

template <class CharT, std::intmax_t N, std::intmax_t D>
CONSTCD14
inline
std::enable_if_t
<
  std::ratio<N, D>::type::den != 1,
  string_literal < CharT, to_string_len(std::ratio<N, D>::type::num) +
                   to_string_len(std::ratio<N, D>::type::den) + 4 >
  >
msl(std::ratio<N, D>) NOEXCEPT {
  using R = typename std::ratio<N, D>::type;
  return msl(CharT{'['}) + msl<R::num>() + msl(CharT{'/'}) +
  msl<R::den>() + msl(CharT{']'});
}

template <class CharT, std::intmax_t N, std::intmax_t D>
CONSTCD14
inline
std::enable_if_t
<
  std::ratio<N, D>::type::den == 1,
  string_literal < CharT, to_string_len(std::ratio<N, D>::type::num) + 3 >
  >
msl(std::ratio<N, D>) NOEXCEPT {
  using R = typename std::ratio<N, D>::type;
  return msl(CharT{'['}) + msl<R::num>() + msl(CharT{']'});
}


#else  // __cplusplus < 201402 || (defined(__EDG_VERSION__) && __EDG_VERSION__ <= 411)

inline
std::string
to_string(std::uint64_t x)
{
  return std::to_string(x);
}

template <class CharT>
inline
std::basic_string<CharT>
to_string(std::uint64_t x)
{
  auto y = std::to_string(x);
  return std::basic_string<CharT>(y.begin(), y.end());
}

template <class CharT, std::intmax_t N, std::intmax_t D>
inline
typename std::enable_if
<
  std::ratio<N, D>::type::den != 1,
  std::basic_string<CharT>
  >::type
msl(std::ratio<N, D>)
{
  using R = typename std::ratio<N, D>::type;
  return std::basic_string<CharT>(1, '[') + to_string<CharT>(R::num) + CharT{'/'} +
         to_string<CharT>(R::den) + CharT{']'};
}

template <class CharT, std::intmax_t N, std::intmax_t D>
inline
typename std::enable_if
<
  std::ratio<N, D>::type::den == 1,
  std::basic_string<CharT>
  >::type
msl(std::ratio<N, D>)
{
  using R = typename std::ratio<N, D>::type;
  return std::basic_string<CharT>(1, '[') + to_string<CharT>(R::num) + CharT{']'};
}

#endif  // __cplusplus < 201402 || (defined(__EDG_VERSION__) && __EDG_VERSION__ <= 411)

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::atto) NOEXCEPT {
  return string_literal<CharT, 2>{'a'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::femto) NOEXCEPT {
  return string_literal<CharT, 2>{'f'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::pico) NOEXCEPT {
  return string_literal<CharT, 2>{'p'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::nano) NOEXCEPT {
  return string_literal<CharT, 2>{'n'};
}

template <class CharT>
CONSTCD11
inline
typename std::enable_if
<
  std::is_same<CharT, char>::value,
  string_literal<char, 3>
  >::type
msl(std::micro) NOEXCEPT {
  return string_literal<char, 3>{'\xC2', '\xB5'};
}

template <class CharT>
CONSTCD11
inline
typename std::enable_if
<
  !std::is_same<CharT, char>::value,
  string_literal<CharT, 2>
  >::type
msl(std::micro) NOEXCEPT {
  return string_literal<CharT, 2>{CharT{static_cast<unsigned char>('\xB5')}};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::milli) NOEXCEPT {
  return string_literal<CharT, 2>{'m'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::centi) NOEXCEPT {
  return string_literal<CharT, 2>{'c'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 3>
msl(std::deca) NOEXCEPT {
  return string_literal<CharT, 3>{'d', 'a'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::deci) NOEXCEPT {
  return string_literal<CharT, 2>{'d'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::hecto) NOEXCEPT {
  return string_literal<CharT, 2>{'h'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::kilo) NOEXCEPT {
  return string_literal<CharT, 2>{'k'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::mega) NOEXCEPT {
  return string_literal<CharT, 2>{'M'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::giga) NOEXCEPT {
  return string_literal<CharT, 2>{'G'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::tera) NOEXCEPT {
  return string_literal<CharT, 2>{'T'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::peta) NOEXCEPT {
  return string_literal<CharT, 2>{'P'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
msl(std::exa) NOEXCEPT {
  return string_literal<CharT, 2>{'E'};
}

template <class CharT, class Period>
CONSTCD11
inline
auto
get_units(Period p)
-> decltype(msl<CharT>(p) + string_literal<CharT, 2> {'s'})
{
  return msl<CharT>(p) + string_literal<CharT, 2> {'s'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
get_units(std::ratio<1>)
{
  return string_literal<CharT, 2> {'s'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
get_units(std::ratio<3600>)
{
  return string_literal<CharT, 2> {'h'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 4>
get_units(std::ratio<60>)
{
  return string_literal<CharT, 4> {'m', 'i', 'n'};
}

template <class CharT>
CONSTCD11
inline
string_literal<CharT, 2>
get_units(std::ratio<86400>)
{
  return string_literal<CharT, 2> {'d'};
}

template <class CharT, class Traits = std::char_traits<CharT>>
struct make_string;

template <>
struct make_string<char> {
  template <class Rep>
  static
  std::string
  from(Rep n)
  {
    return std::to_string(n);
  }
};

template <class Traits>
struct make_string<char, Traits> {
  template <class Rep>
  static
  std::basic_string<char, Traits>
  from(Rep n)
  {
    auto s = std::to_string(n);
    return std::basic_string<char, Traits>(s.begin(), s.end());
  }
};

template <>
struct make_string<wchar_t> {
  template <class Rep>
  static
  std::wstring
  from(Rep n)
  {
    return std::to_wstring(n);
  }
};

template <class Traits>
struct make_string<wchar_t, Traits> {
  template <class Rep>
  static
  std::basic_string<wchar_t, Traits>
  from(Rep n)
  {
    auto s = std::to_wstring(n);
    return std::basic_string<wchar_t, Traits>(s.begin(), s.end());
  }
};

}  // namespace detail

// to_stream

CONSTDATA year nanyear{-32768};

template <class Duration>
struct fields {
  year_month_day        ymd{nanyear / 0 / 0};
  weekday               wd{8u};
  hh_mm_ss<Duration>    tod{};
  bool                  has_tod = false;

  fields() = default;

  fields(year_month_day ymd_) : ymd(ymd_) {}
  fields(weekday wd_) : wd(wd_) {}
  fields(hh_mm_ss<Duration> tod_) : tod(tod_), has_tod(true) {}

  fields(year_month_day ymd_, weekday wd_) : ymd(ymd_), wd(wd_) {}
  fields(year_month_day ymd_, hh_mm_ss<Duration> tod_) : ymd(ymd_), tod(tod_),
    has_tod(true) {}

  fields(weekday wd_, hh_mm_ss<Duration> tod_) : wd(wd_), tod(tod_),
    has_tod(true) {}

  fields(year_month_day ymd_, weekday wd_, hh_mm_ss<Duration> tod_)
    : ymd(ymd_)
    , wd(wd_)
    , tod(tod_)
    , has_tod(true)
  {}
};

namespace detail {

template <class CharT, class Traits, class Duration>
unsigned
extract_weekday(std::basic_ostream<CharT, Traits> &os,
                const fields<Duration> &fds)
{
  if (!fds.ymd.ok() && !fds.wd.ok()) {
    // fds does not contain a valid weekday
    os.setstate(std::ios::failbit);
    return 8;
  }
  weekday wd;
  if (fds.ymd.ok()) {
    wd = weekday{sys_days(fds.ymd)};
    if (fds.wd.ok() && wd != fds.wd) {
      // fds.ymd and fds.wd are inconsistent
      os.setstate(std::ios::failbit);
      return 8;
    }
  }
  else {
    wd = fds.wd;
  }
  return static_cast<unsigned>((wd - Sunday).count());
}

template <class CharT, class Traits, class Duration>
unsigned
extract_month(std::basic_ostream<CharT, Traits> &os,
              const fields<Duration> &fds)
{
  if (!fds.ymd.month().ok()) {
    // fds does not contain a valid month
    os.setstate(std::ios::failbit);
    return 0;
  }
  return static_cast<unsigned>(fds.ymd.month());
}

}  // namespace detail

#if ONLY_C_LOCALE

namespace detail {

inline
std::pair<const std::string *, const std::string *>
weekday_names()
{
  static const std::string nm[] = {
    "Sunday",
    "Monday",
    "Tuesday",
    "Wednesday",
    "Thursday",
    "Friday",
    "Saturday",
    "Sun",
    "Mon",
    "Tue",
    "Wed",
    "Thu",
    "Fri",
    "Sat"
  };
  return std::make_pair(nm, nm + sizeof(nm) / sizeof(nm[0]));
}

inline
std::pair<const std::string *, const std::string *>
month_names()
{
  static const std::string nm[] = {
    "January",
    "February",
    "March",
    "April",
    "May",
    "June",
    "July",
    "August",
    "September",
    "October",
    "November",
    "December",
    "Jan",
    "Feb",
    "Mar",
    "Apr",
    "May",
    "Jun",
    "Jul",
    "Aug",
    "Sep",
    "Oct",
    "Nov",
    "Dec"
  };
  return std::make_pair(nm, nm + sizeof(nm) / sizeof(nm[0]));
}

inline
std::pair<const std::string *, const std::string *>
ampm_names()
{
  static const std::string nm[] = {
    "AM",
    "PM"
  };
  return std::make_pair(nm, nm + sizeof(nm) / sizeof(nm[0]));
}

template <class CharT, class Traits, class FwdIter>
FwdIter
scan_keyword(std::basic_istream<CharT, Traits> &is, FwdIter kb, FwdIter ke)
{
  size_t nkw = static_cast<size_t>(std::distance(kb, ke));
  const unsigned char doesnt_match = '\0';
  const unsigned char might_match = '\1';
  const unsigned char does_match = '\2';
  unsigned char statbuf[100];
  unsigned char *status = statbuf;
  std::unique_ptr<unsigned char, void(*)(void *)> stat_hold(0, free);
  if (nkw > sizeof(statbuf)) {
    status = (unsigned char *)std::malloc(nkw);
    if (status == nullptr) {
      throw std::bad_alloc();
    }
    stat_hold.reset(status);
  }
  size_t n_might_match = nkw;  // At this point, any keyword might match
  size_t n_does_match = 0;     // but none of them definitely do
  // Initialize all statuses to might_match, except for "" keywords are does_match
  unsigned char *st = status;
  for (auto ky = kb; ky != ke; ++ky, ++st) {
    if (!ky->empty()) {
      *st = might_match;
    }
    else {
      *st = does_match;
      --n_might_match;
      ++n_does_match;
    }
  }
  // While there might be a match, test keywords against the next CharT
  for (size_t indx = 0; is && n_might_match > 0; ++indx) {
    // Peek at the next CharT but don't consume it
    auto ic = is.peek();
    if (ic == EOF) {
      is.setstate(std::ios::eofbit);
      break;
    }
    auto c = static_cast<char>(toupper(ic));
    bool consume = false;
    // For each keyword which might match, see if the indx character is c
    // If a match if found, consume c
    // If a match is found, and that is the last character in the keyword,
    //    then that keyword matches.
    // If the keyword doesn't match this character, then change the keyword
    //    to doesn't match
    st = status;
    for (auto ky = kb; ky != ke; ++ky, ++st) {
      if (*st == might_match) {
        if (c == static_cast<char>(toupper((*ky)[indx]))) {
          consume = true;
          if (ky->size() == indx + 1) {
            *st = does_match;
            --n_might_match;
            ++n_does_match;
          }
        }
        else {
          *st = doesnt_match;
          --n_might_match;
        }
      }
    }
    // consume if we matched a character
    if (consume) {
      (void)is.get();
      // If we consumed a character and there might be a matched keyword that
      //   was marked matched on a previous iteration, then such keywords
      //   are now marked as not matching.
      if (n_might_match + n_does_match > 1) {
        st = status;
        for (auto ky = kb; ky != ke; ++ky, ++st) {
          if (*st == does_match && ky->size() != indx + 1) {
            *st = doesnt_match;
            --n_does_match;
          }
        }
      }
    }
  }
  // We've exited the loop because we hit eof and/or we have no more "might matches".
  // Return the first matching result
  for (st = status; kb != ke; ++kb, ++st)
    if (*st == does_match) {
      break;
    }
  if (kb == ke) {
    is.setstate(std::ios::failbit);
  }
  return kb;
}

}  // namespace detail

#endif  // ONLY_C_LOCALE

template <class CharT, class Traits, class Duration>
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const fields<Duration> &fds, const std::string *abbrev,
          const std::chrono::seconds *offset_sec)
{
#if ONLY_C_LOCALE
  using detail::weekday_names;
  using detail::month_names;
  using detail::ampm_names;
#endif
  using detail::save_ostream;
  using detail::get_units;
  using detail::extract_weekday;
  using detail::extract_month;
  using std::ios;
  using std::chrono::duration_cast;
  using std::chrono::seconds;
  using std::chrono::minutes;
  using std::chrono::hours;
  date::detail::save_ostream<CharT, Traits> ss(os);
  os.fill(' ');
  os.flags(std::ios::skipws | std::ios::dec);
  os.width(0);
  tm tm{};
  bool insert_negative = fds.has_tod && fds.tod.to_duration() < Duration::zero();
#if !ONLY_C_LOCALE
  auto &facet = std::use_facet<std::time_put<CharT>>(os.getloc());
#endif
  const CharT *command = nullptr;
  CharT modified = CharT{};
  for (; *fmt; ++fmt) {
    switch (*fmt) {
    case 'a':
    case 'A':
      if (command) {
        if (modified == CharT{}) {
          tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
          if (os.fail()) {
            return os;
          }
#if !ONLY_C_LOCALE
          const CharT f[] = {'%', *fmt};
          facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
#else  // ONLY_C_LOCALE
          os << weekday_names().first[tm.tm_wday + 7 * (*fmt == 'a')];
#endif  // ONLY_C_LOCALE
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'b':
    case 'B':
    case 'h':
      if (command) {
        if (modified == CharT{}) {
          tm.tm_mon = static_cast<int>(extract_month(os, fds)) - 1;
#if !ONLY_C_LOCALE
          const CharT f[] = {'%', *fmt};
          facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
#else  // ONLY_C_LOCALE
          os << month_names().first[tm.tm_mon + 12 * (*fmt != 'B')];
#endif  // ONLY_C_LOCALE
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'c':
    case 'x':
      if (command) {
        if (modified == CharT{'O'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.ymd.ok()) {
            os.setstate(std::ios::failbit);
          }
          if (*fmt == 'c' && !fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
#if !ONLY_C_LOCALE
          tm = std::tm {};
          auto const &ymd = fds.ymd;
          auto ld = local_days(ymd);
          if (*fmt == 'c') {
            tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
            tm.tm_min = static_cast<int>(fds.tod.minutes().count());
            tm.tm_hour = static_cast<int>(fds.tod.hours().count());
          }
          tm.tm_mday = static_cast<int>(static_cast<unsigned>(ymd.day()));
          tm.tm_mon = static_cast<int>(extract_month(os, fds) - 1);
          tm.tm_year = static_cast<int>(ymd.year()) - 1900;
          tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
          if (os.fail()) {
            return os;
          }
          tm.tm_yday = static_cast<int>((ld - local_days(ymd.year() / 1 / 1)).count());
          CharT f[3] = {'%'};
          auto fe = std::begin(f) + 1;
          if (modified == CharT{'E'})
            *fe++ = modified;
          *fe++ = *fmt;
          facet.put(os, os, os.fill(), &tm, std::begin(f), fe);
#else  // ONLY_C_LOCALE
          if (*fmt == 'c') {
            auto wd = static_cast<int>(extract_weekday(os, fds));
            os << weekday_names().first[static_cast<unsigned>(wd) + 7]
               << ' ';
            os << month_names().first[extract_month(os, fds) - 1 + 12] << ' ';
            auto d = static_cast<int>(static_cast<unsigned>(fds.ymd.day()));
            if (d < 10) {
              os << ' ';
            }
            os << d << ' '
               << make_time(duration_cast<seconds>(fds.tod.to_duration()))
               << ' ' << fds.ymd.year();

          }
          else { // *fmt == 'x'
            auto const &ymd = fds.ymd;
            save_ostream<CharT, Traits> _(os);
            os.fill('0');
            os.flags(std::ios::dec | std::ios::right);
            os.width(2);
            os << static_cast<unsigned>(ymd.month()) << CharT{'/'};
            os.width(2);
            os << static_cast<unsigned>(ymd.day()) << CharT{'/'};
            os.width(2);
            os << static_cast<int>(ymd.year()) % 100;
          }
#endif  // ONLY_C_LOCALE
        }
        command = nullptr;
        modified = CharT{};
      }
      else {
        os << *fmt;
      }
      break;
    case 'C':
      if (command) {
        if (modified == CharT{'O'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.ymd.year().ok()) {
            os.setstate(std::ios::failbit);
          }
          auto y = static_cast<int>(fds.ymd.year());
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            save_ostream<CharT, Traits> _(os);
            os.fill('0');
            os.flags(std::ios::dec | std::ios::right);
            if (y >= 0) {
              os.width(2);
              os << y / 100;
            }
            else {
              os << CharT{'-'};
              os.width(2);
              os << -(y - 99) / 100;
            }
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'E'}) {
            tm.tm_year = y - 1900;
            CharT f[3] = {'%', 'E', 'C'};
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        command = nullptr;
        modified = CharT{};
      }
      else {
        os << *fmt;
      }
      break;
    case 'd':
    case 'e':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.ymd.day().ok()) {
            os.setstate(std::ios::failbit);
          }
          auto d = static_cast<int>(static_cast<unsigned>(fds.ymd.day()));
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            save_ostream<CharT, Traits> _(os);
            if (*fmt == CharT{'d'})
              os.fill('0');
            else {
              os.fill(' ');
            }
            os.flags(std::ios::dec | std::ios::right);
            os.width(2);
            os << d;
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            tm.tm_mday = d;
            CharT f[3] = {'%', 'O', *fmt};
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        command = nullptr;
        modified = CharT{};
      }
      else {
        os << *fmt;
      }
      break;
    case 'D':
      if (command) {
        if (modified == CharT{}) {
          if (!fds.ymd.ok()) {
            os.setstate(std::ios::failbit);
          }
          auto const &ymd = fds.ymd;
          save_ostream<CharT, Traits> _(os);
          os.fill('0');
          os.flags(std::ios::dec | std::ios::right);
          os.width(2);
          os << static_cast<unsigned>(ymd.month()) << CharT{'/'};
          os.width(2);
          os << static_cast<unsigned>(ymd.day()) << CharT{'/'};
          os.width(2);
          os << static_cast<int>(ymd.year()) % 100;
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'F':
      if (command) {
        if (modified == CharT{}) {
          if (!fds.ymd.ok()) {
            os.setstate(std::ios::failbit);
          }
          auto const &ymd = fds.ymd;
          save_ostream<CharT, Traits> _(os);
          os.fill('0');
          os.flags(std::ios::dec | std::ios::right);
          os.width(4);
          os << static_cast<int>(ymd.year()) << CharT{'-'};
          os.width(2);
          os << static_cast<unsigned>(ymd.month()) << CharT{'-'};
          os.width(2);
          os << static_cast<unsigned>(ymd.day());
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'g':
    case 'G':
      if (command) {
        if (modified == CharT{}) {
          if (!fds.ymd.ok()) {
            os.setstate(std::ios::failbit);
          }
          auto ld = local_days(fds.ymd);
          auto y = year_month_day{ld + days{3}}.year();
          auto start = local_days((y - years{1}) / December / Thursday[last]) +
                       (Monday - Thursday);
          if (ld < start) {
            --y;
          }
          if (*fmt == CharT{'G'})
            os << y;
          else {
            save_ostream<CharT, Traits> _(os);
            os.fill('0');
            os.flags(std::ios::dec | std::ios::right);
            os.width(2);
            os << std::abs(static_cast<int>(y)) % 100;
          }
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'H':
    case 'I':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
          if (insert_negative) {
            os << '-';
            insert_negative = false;
          }
          auto hms = fds.tod;
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            auto h = *fmt == CharT{'I'} ? make12(hms.hours()) : hms.hours();
            if (h < hours{10})
              os << CharT{'0'};
            os << h.count();
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            const CharT f[] = {'%', modified, *fmt};
            tm.tm_hour = static_cast<int>(hms.hours().count());
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'j':
      if (command) {
        if (modified == CharT{}) {
          if (fds.ymd.ok() || fds.has_tod) {
            days doy;
            if (fds.ymd.ok()) {
              auto ld = local_days(fds.ymd);
              auto y = fds.ymd.year();
              doy = ld - local_days(y / January / 1) + days{1};
            }
            else {
              doy = duration_cast<days>(fds.tod.to_duration());
            }
            save_ostream<CharT, Traits> _(os);
            os.fill('0');
            os.flags(std::ios::dec | std::ios::right);
            os.width(3);
            os << doy.count();
          }
          else {
            os.setstate(std::ios::failbit);
          }
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'm':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.ymd.month().ok()) {
            os.setstate(std::ios::failbit);
          }
          auto m = static_cast<unsigned>(fds.ymd.month());
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            if (m < 10)
              os << CharT{'0'};
            os << m;
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            const CharT f[] = {'%', modified, *fmt};
            tm.tm_mon = static_cast<int>(m - 1);
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'M':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
          if (insert_negative) {
            os << '-';
            insert_negative = false;
          }
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            if (fds.tod.minutes() < minutes{10})
              os << CharT{'0'};
            os << fds.tod.minutes().count();
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            const CharT f[] = {'%', modified, *fmt};
            tm.tm_min = static_cast<int>(fds.tod.minutes().count());
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'n':
      if (command) {
        if (modified == CharT{})
          os << CharT{'\n'};
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'p':
      if (command) {
        if (modified == CharT{}) {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
#if !ONLY_C_LOCALE
          const CharT f[] = {'%', *fmt};
          tm.tm_hour = static_cast<int>(fds.tod.hours().count());
          facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
#else
          if (is_am(fds.tod.hours())) {
            os << ampm_names().first[0];
          }
          else {
            os << ampm_names().first[1];
          }
#endif
        }
        else {
          os << CharT{'%'} << modified << *fmt;
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'Q':
    case 'q':
      if (command) {
        if (modified == CharT{}) {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
          auto d = fds.tod.to_duration();
          if (*fmt == 'q')
            os << get_units<CharT>(typename decltype(d)::period::type{});
          else {
            os << d.count();
          }
        }
        else {
          os << CharT{'%'} << modified << *fmt;
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'r':
      if (command) {
        if (modified == CharT{}) {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
#if !ONLY_C_LOCALE
          const CharT f[] = {'%', *fmt};
          tm.tm_hour = static_cast<int>(fds.tod.hours().count());
          tm.tm_min = static_cast<int>(fds.tod.minutes().count());
          tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
          facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
#else
          hh_mm_ss<seconds> tod(duration_cast<seconds>(fds.tod.to_duration()));
          save_ostream<CharT, Traits> _(os);
          os.fill('0');
          os.width(2);
          os << make12(tod.hours()).count() << CharT{':'};
          os.width(2);
          os << tod.minutes().count() << CharT{':'};
          os.width(2);
          os << tod.seconds().count() << CharT{' '};
          if (is_am(tod.hours())) {
            os << ampm_names().first[0];
          }
          else {
            os << ampm_names().first[1];
          }
#endif
        }
        else {
          os << CharT{'%'} << modified << *fmt;
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'R':
      if (command) {
        if (modified == CharT{}) {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
          if (fds.tod.hours() < hours{10})
            os << CharT{'0'};
          os << fds.tod.hours().count() << CharT{':'};
          if (fds.tod.minutes() < minutes{10})
            os << CharT{'0'};
          os << fds.tod.minutes().count();
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'S':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
          if (insert_negative) {
            os << '-';
            insert_negative = false;
          }
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            os << fds.tod.s_;
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            const CharT f[] = {'%', modified, *fmt};
            tm.tm_sec = static_cast<int>(fds.tod.s_.seconds().count());
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 't':
      if (command) {
        if (modified == CharT{})
          os << CharT{'\t'};
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'T':
      if (command) {
        if (modified == CharT{}) {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
          os << fds.tod;
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'u':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          auto wd = extract_weekday(os, fds);
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            os << (wd != 0 ? wd : 7u);
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            const CharT f[] = {'%', modified, *fmt};
            tm.tm_wday = static_cast<int>(wd);
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'U':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          auto const &ymd = fds.ymd;
          if (!ymd.ok()) {
            os.setstate(std::ios::failbit);
          }
          auto ld = local_days(ymd);
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            auto st = local_days(Sunday[1] / January / ymd.year());
            if (ld < st)
              os << CharT{'0'} << CharT{'0'};
            else {
              auto wn = duration_cast<weeks>(ld - st).count() + 1;
              if (wn < 10)
                os << CharT{'0'};
              os << wn;
            }
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            const CharT f[] = {'%', modified, *fmt};
            tm.tm_year = static_cast<int>(ymd.year()) - 1900;
            tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
            if (os.fail()) {
              return os;
            }
            tm.tm_yday = static_cast<int>((ld - local_days(ymd.year() / 1 / 1)).count());
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'V':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.ymd.ok()) {
            os.setstate(std::ios::failbit);
          }
          auto ld = local_days(fds.ymd);
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            auto y = year_month_day{ld + days{3}}.year();
            auto st = local_days((y - years{1}) / 12 / Thursday[last]) +
                      (Monday - Thursday);
            if (ld < st) {
              --y;
              st = local_days((y - years{1}) / 12 / Thursday[last]) +
                   (Monday - Thursday);
            }
            auto wn = duration_cast<weeks>(ld - st).count() + 1;
            if (wn < 10)
              os << CharT{'0'};
            os << wn;
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            const CharT f[] = {'%', modified, *fmt};
            auto const &ymd = fds.ymd;
            tm.tm_year = static_cast<int>(ymd.year()) - 1900;
            tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
            if (os.fail()) {
              return os;
            }
            tm.tm_yday = static_cast<int>((ld - local_days(ymd.year() / 1 / 1)).count());
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'w':
      if (command) {
        auto wd = extract_weekday(os, fds);
        if (os.fail()) {
          return os;
        }
#if !ONLY_C_LOCALE
        if (modified == CharT {})
#else
        if (modified != CharT {'E'})
#endif
        {
          os << wd;
        }
#if !ONLY_C_LOCALE
        else if (modified == CharT {'O'}) {
          const CharT f[] = {'%', modified, *fmt};
          tm.tm_wday = static_cast<int>(wd);
          facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
        }
#endif
        else {
          os << CharT{'%'} << modified << *fmt;
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'W':
      if (command) {
        if (modified == CharT{'E'})
          os << CharT{'%'} << modified << *fmt;
        else {
          auto const &ymd = fds.ymd;
          if (!ymd.ok()) {
            os.setstate(std::ios::failbit);
          }
          auto ld = local_days(ymd);
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            auto st = local_days(Monday[1] / January / ymd.year());
            if (ld < st)
              os << CharT{'0'} << CharT{'0'};
            else {
              auto wn = duration_cast<weeks>(ld - st).count() + 1;
              if (wn < 10)
                os << CharT{'0'};
              os << wn;
            }
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            const CharT f[] = {'%', modified, *fmt};
            tm.tm_year = static_cast<int>(ymd.year()) - 1900;
            tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
            if (os.fail()) {
              return os;
            }
            tm.tm_yday = static_cast<int>((ld - local_days(ymd.year() / 1 / 1)).count());
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'X':
      if (command) {
        if (modified == CharT{'O'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.has_tod) {
            os.setstate(std::ios::failbit);
          }
#if !ONLY_C_LOCALE
          tm = std::tm {};
          tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
          tm.tm_min = static_cast<int>(fds.tod.minutes().count());
          tm.tm_hour = static_cast<int>(fds.tod.hours().count());
          CharT f[3] = {'%'};
          auto fe = std::begin(f) + 1;
          if (modified == CharT{'E'})
            *fe++ = modified;
          *fe++ = *fmt;
          facet.put(os, os, os.fill(), &tm, std::begin(f), fe);
#else
          os << fds.tod;
#endif
        }
        command = nullptr;
        modified = CharT{};
      }
      else {
        os << *fmt;
      }
      break;
    case 'y':
      if (command) {
        if (!fds.ymd.year().ok()) {
          os.setstate(std::ios::failbit);
        }
        auto y = static_cast<int>(fds.ymd.year());
#if !ONLY_C_LOCALE
        if (modified == CharT {}) {
#endif
          y = std::abs(y) % 100;
          if (y < 10)
            os << CharT{'0'};
          os << y;
#if !ONLY_C_LOCALE
        }
        else {
          const CharT f[] = {'%', modified, *fmt};
          tm.tm_year = y - 1900;
          facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
        }
#endif
        modified = CharT {};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'Y':
      if (command) {
        if (modified == CharT{'O'})
          os << CharT{'%'} << modified << *fmt;
        else {
          if (!fds.ymd.year().ok()) {
            os.setstate(std::ios::failbit);
          }
          auto y = fds.ymd.year();
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            os << y;
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'E'}) {
            const CharT f[] = {'%', modified, *fmt};
            tm.tm_year = static_cast<int>(y) - 1900;
            facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
          }
#endif
        }
        modified = CharT{};
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'z':
      if (command) {
        if (offset_sec == nullptr) {
          // Can not format %z with unknown offset
          os.setstate(ios::failbit);
          return os;
        }
        auto m = duration_cast<minutes>(*offset_sec);
        auto neg = m < minutes{0};
        m = date::abs(m);
        auto h = duration_cast<hours>(m);
        m -= h;
        if (neg)
          os << CharT{'-'};
        else
          os << CharT{'+'};
        if (h < hours{10})
          os << CharT{'0'};
        os << h.count();
        if (modified != CharT{})
          os << CharT{':'};
        if (m < minutes{10})
          os << CharT{'0'};
        os << m.count();
        command = nullptr;
        modified = CharT{};
      }
      else {
        os << *fmt;
      }
      break;
    case 'Z':
      if (command) {
        if (modified == CharT{}) {
          if (abbrev == nullptr) {
            // Can not format %Z with unknown time_zone
            os.setstate(ios::failbit);
            return os;
          }
          for (auto c : *abbrev) {
            os << CharT(c);
          }
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          modified = CharT{};
        }
        command = nullptr;
      }
      else {
        os << *fmt;
      }
      break;
    case 'E':
    case 'O':
      if (command) {
        if (modified == CharT{}) {
          modified = *fmt;
        }
        else {
          os << CharT{'%'} << modified << *fmt;
          command = nullptr;
          modified = CharT{};
        }
      }
      else {
        os << *fmt;
      }
      break;
    case '%':
      if (command) {
        if (modified == CharT{}) {
          os << CharT{'%'};
          command = nullptr;
        }
        else {
          os << CharT{'%'} << modified << CharT{'%'};
          command = nullptr;
          modified = CharT{};
        }
      }
      else {
        command = fmt;
      }
      break;
    default:
      if (command) {
        os << CharT{'%'};
        command = nullptr;
      }
      if (modified != CharT{}) {
        os << modified;
        modified = CharT{};
      }
      os << *fmt;
      break;
    }
  }
  if (command)
    os << CharT{'%'};
  if (modified != CharT{})
    os << modified;
  return os;
}

template <class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const year &y)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{y / 0 / 0};
  return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const month &m)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{m / 0 / nanyear};
  return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt, const day &d)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{d / 0 / nanyear};
  return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const weekday &wd)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{wd};
  return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const year_month &ym)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{ym / 0};
  return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const month_day &md)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{md / nanyear};
  return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const year_month_day &ymd)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{ymd};
  return to_stream(os, fmt, fds);
}

template <class CharT, class Traits, class Rep, class Period>
inline
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const std::chrono::duration<Rep, Period> &d)
{
  using Duration = std::chrono::duration<Rep, Period>;
  using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
  fields<CT> fds{hh_mm_ss<CT>{d}};
  return to_stream(os, fmt, fds);
}

template <class CharT, class Traits, class Duration>
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const local_time<Duration> &tp, const std::string *abbrev = nullptr,
          const std::chrono::seconds *offset_sec = nullptr)
{
  using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
  auto ld = floor<days>(tp);
  fields<CT> fds{year_month_day{ld}, hh_mm_ss<CT>{tp - local_seconds{ld}}};
  return to_stream(os, fmt, fds, abbrev, offset_sec);
}

template <class CharT, class Traits, class Duration>
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const sys_time<Duration> &tp)
{
  using std::chrono::seconds;
  using CT = typename std::common_type<Duration, seconds>::type;
  const std::string abbrev("UTC");
  CONSTDATA seconds offset{0};
  auto sd = floor<days>(tp);
  fields<CT> fds{year_month_day{sd}, hh_mm_ss<CT>{tp - sys_seconds{sd}}};
  return to_stream(os, fmt, fds, &abbrev, &offset);
}

// format

template <class CharT, class Streamable>
auto
format(const std::locale &loc, const CharT *fmt, const Streamable &tp)
-> decltype(to_stream(std::declval<std::basic_ostream<CharT>&>(), fmt, tp),
std::basic_string<CharT> {})
{
  std::basic_ostringstream<CharT> os;
  os.exceptions(std::ios::failbit | std::ios::badbit);
  os.imbue(loc);
  to_stream(os, fmt, tp);
  return os.str();
}

template <class CharT, class Streamable>
auto
format(const CharT *fmt, const Streamable &tp)
-> decltype(to_stream(std::declval<std::basic_ostream<CharT>&>(), fmt, tp),
std::basic_string<CharT> {})
{
  std::basic_ostringstream<CharT> os;
  os.exceptions(std::ios::failbit | std::ios::badbit);
  to_stream(os, fmt, tp);
  return os.str();
}

template <class CharT, class Traits, class Alloc, class Streamable>
auto
format(const std::locale &loc,
       const std::basic_string<CharT, Traits, Alloc> &fmt,
       const Streamable &tp)
-> decltype(to_stream(std::declval<std::basic_ostream<CharT, Traits>&>(),
                      fmt.c_str(), tp),
std::basic_string<CharT, Traits, Alloc> {})
{
  std::basic_ostringstream<CharT, Traits, Alloc> os;
  os.exceptions(std::ios::failbit | std::ios::badbit);
  os.imbue(loc);
  to_stream(os, fmt.c_str(), tp);
  return os.str();
}

template <class CharT, class Traits, class Alloc, class Streamable>
auto
format(const std::basic_string<CharT, Traits, Alloc> &fmt, const Streamable &tp)
-> decltype(to_stream(std::declval<std::basic_ostream<CharT, Traits>&>(),
                      fmt.c_str(), tp),
std::basic_string<CharT, Traits, Alloc> {})
{
  std::basic_ostringstream<CharT, Traits, Alloc> os;
  os.exceptions(std::ios::failbit | std::ios::badbit);
  to_stream(os, fmt.c_str(), tp);
  return os.str();
}

// parse

namespace detail {

template <class CharT, class Traits>
bool
read_char(std::basic_istream<CharT, Traits> &is, CharT fmt,
          std::ios::iostate &err)
{
  auto ic = is.get();
  if (Traits::eq_int_type(ic, Traits::eof()) ||
      !Traits::eq(Traits::to_char_type(ic), fmt)) {
    err |= std::ios::failbit;
    is.setstate(std::ios::failbit);
    return false;
  }
  return true;
}

template <class CharT, class Traits>
unsigned
read_unsigned(std::basic_istream<CharT, Traits> &is, unsigned m = 1,
              unsigned M = 10)
{
  unsigned x = 0;
  unsigned count = 0;
  while (true) {
    auto ic = is.peek();
    if (Traits::eq_int_type(ic, Traits::eof())) {
      break;
    }
    auto c = static_cast<char>(Traits::to_char_type(ic));
    if (!('0' <= c && c <= '9')) {
      break;
    }
    (void)is.get();
    ++count;
    x = 10 * x + static_cast<unsigned>(c - '0');
    if (count == M) {
      break;
    }
  }
  if (count < m) {
    is.setstate(std::ios::failbit);
  }
  return x;
}

template <class CharT, class Traits>
int
read_signed(std::basic_istream<CharT, Traits> &is, unsigned m = 1,
            unsigned M = 10)
{
  auto ic = is.peek();
  if (!Traits::eq_int_type(ic, Traits::eof())) {
    auto c = static_cast<char>(Traits::to_char_type(ic));
    if (('0' <= c && c <= '9') || c == '-' || c == '+') {
      if (c == '-' || c == '+') {
        (void)is.get();
      }
      auto x = static_cast<int>(read_unsigned(is, std::max(m, 1u), M));
      if (!is.fail()) {
        if (c == '-') {
          x = -x;
        }
        return x;
      }
    }
  }
  if (m > 0) {
    is.setstate(std::ios::failbit);
  }
  return 0;
}

template <class CharT, class Traits>
long double
read_long_double(std::basic_istream<CharT, Traits> &is, unsigned m = 1,
                 unsigned M = 10)
{
  unsigned count = 0;
  auto decimal_point = Traits::to_int_type(
                         std::use_facet<std::numpunct<CharT>>(is.getloc()).decimal_point());
  std::string buf;
  while (true) {
    auto ic = is.peek();
    if (Traits::eq_int_type(ic, Traits::eof())) {
      break;
    }
    if (Traits::eq_int_type(ic, decimal_point)) {
      buf += '.';
      decimal_point = Traits::eof();
      is.get();
    }
    else {
      auto c = static_cast<char>(Traits::to_char_type(ic));
      if (!('0' <= c && c <= '9')) {
        break;
      }
      buf += c;
      (void)is.get();
    }
    if (++count == M) {
      break;
    }
  }
  if (count < m) {
    is.setstate(std::ios::failbit);
    return 0;
  }
  return std::stold(buf);
}

struct rs {
  int &i;
  unsigned m;
  unsigned M;
};

struct ru {
  int &i;
  unsigned m;
  unsigned M;
};

struct rld {
  long double &i;
  unsigned m;
  unsigned M;
};

template <class CharT, class Traits>
void
read(std::basic_istream<CharT, Traits> &)
{
}

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, CharT a0, Args &&...args);

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, rs a0, Args &&...args);

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, ru a0, Args &&...args);

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, int a0, Args &&...args);

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, rld a0, Args &&...args);

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, CharT a0, Args &&...args)
{
  // No-op if a0 == CharT{}
  if (a0 != CharT{}) {
    auto ic = is.peek();
    if (Traits::eq_int_type(ic, Traits::eof())) {
      is.setstate(std::ios::failbit | std::ios::eofbit);
      return;
    }
    if (!Traits::eq(Traits::to_char_type(ic), a0)) {
      is.setstate(std::ios::failbit);
      return;
    }
    (void)is.get();
  }
  read(is, std::forward<Args>(args)...);
}

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, rs a0, Args &&...args)
{
  auto x = read_signed(is, a0.m, a0.M);
  if (is.fail()) {
    return;
  }
  a0.i = x;
  read(is, std::forward<Args>(args)...);
}

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, ru a0, Args &&...args)
{
  auto x = read_unsigned(is, a0.m, a0.M);
  if (is.fail()) {
    return;
  }
  a0.i = static_cast<int>(x);
  read(is, std::forward<Args>(args)...);
}

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, int a0, Args &&...args)
{
  if (a0 != -1) {
    auto u = static_cast<unsigned>(a0);
    CharT buf[std::numeric_limits<unsigned>::digits10 + 2] = {};
    auto e = buf;
    do {
      *e++ = static_cast<CharT>(CharT(u % 10) + CharT{'0'});
      u /= 10;
    }
    while (u > 0);
    std::reverse(buf, e);
    for (auto p = buf; p != e && is.rdstate() == std::ios::goodbit; ++p) {
      read(is, *p);
    }
  }
  if (is.rdstate() == std::ios::goodbit) {
    read(is, std::forward<Args>(args)...);
  }
}

template <class CharT, class Traits, class ...Args>
void
read(std::basic_istream<CharT, Traits> &is, rld a0, Args &&...args)
{
  auto x = read_long_double(is, a0.m, a0.M);
  if (is.fail()) {
    return;
  }
  a0.i = x;
  read(is, std::forward<Args>(args)...);
}

template <class T, class CharT, class Traits>
inline
void
checked_set(T &value, T from, T not_a_value, std::basic_ios<CharT, Traits> &is)
{
  if (!is.fail()) {
    if (value == not_a_value) {
      value = std::move(from);
    }
    else if (value != from) {
      is.setstate(std::ios::failbit);
    }
  }
}

}  // namespace detail;

template <class CharT, class Traits, class Duration, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            fields<Duration> &fds, std::basic_string<CharT, Traits, Alloc> *abbrev,
            std::chrono::minutes *offset)
{
  using std::numeric_limits;
  using std::ios;
  using std::chrono::duration;
  using std::chrono::duration_cast;
  using std::chrono::seconds;
  using std::chrono::minutes;
  using std::chrono::hours;
  typename std::basic_istream<CharT, Traits>::sentry ok{is, true};
  if (ok) {
    date::detail::save_istream<CharT, Traits> ss(is);
    is.fill(' ');
    is.flags(std::ios::skipws | std::ios::dec);
    is.width(0);
#if !ONLY_C_LOCALE
    auto &f = std::use_facet<std::time_get<CharT>>(is.getloc());
    std::tm tm{};
#endif
    const CharT *command = nullptr;
    auto modified = CharT{};
    auto width = -1;

    CONSTDATA int not_a_year = numeric_limits<int>::min();
    CONSTDATA int not_a_2digit_year = 100;
    CONSTDATA int not_a_century = not_a_year / 100;
    CONSTDATA int not_a_month = 0;
    CONSTDATA int not_a_day = 0;
    CONSTDATA int not_a_hour = numeric_limits<int>::min();
    CONSTDATA int not_a_hour_12_value = 0;
    CONSTDATA int not_a_minute = not_a_hour;
    CONSTDATA Duration not_a_second = Duration::min();
    CONSTDATA int not_a_doy = -1;
    CONSTDATA int not_a_weekday = 8;
    CONSTDATA int not_a_week_num = 100;
    CONSTDATA int not_a_ampm = -1;
    CONSTDATA minutes not_a_offset = minutes::min();

    int Y = not_a_year;             // c, F, Y                   *
    int y = not_a_2digit_year;      // D, x, y                   *
    int g = not_a_2digit_year;      // g                         *
    int G = not_a_year;             // G                         *
    int C = not_a_century;          // C                         *
    int m = not_a_month;            // b, B, h, m, c, D, F, x    *
    int d = not_a_day;              // c, d, D, e, F, x          *
    int j = not_a_doy;              // j                         *
    int wd = not_a_weekday;         // a, A, u, w                *
    int H = not_a_hour;             // c, H, R, T, X             *
    int I = not_a_hour_12_value;    // I, r                      *
    int p = not_a_ampm;             // p, r                      *
    int M = not_a_minute;           // c, M, r, R, T, X          *
    Duration s = not_a_second;      // c, r, S, T, X             *
    int U = not_a_week_num;         // U                         *
    int V = not_a_week_num;         // V                         *
    int W = not_a_week_num;         // W                         *
    std::basic_string<CharT, Traits, Alloc> temp_abbrev;  // Z   *
    minutes temp_offset = not_a_offset;  // z                    *

    using detail::read;
    using detail::rs;
    using detail::ru;
    using detail::rld;
    using detail::checked_set;
    for (; *fmt != CharT{} && !is.fail(); ++fmt) {
      switch (*fmt) {
      case 'a':
      case 'A':
      case 'u':
      case 'w':  // wd:  a, A, u, w
        if (command) {
          int trial_wd = not_a_weekday;
          if (*fmt == 'a' || *fmt == 'A') {
            if (modified == CharT{}) {
#if !ONLY_C_LOCALE
              ios::iostate err = ios::goodbit;
              f.get(is, nullptr, is, err, &tm, command, fmt + 1);
              is.setstate(err);
              if (!is.fail()) {
                trial_wd = tm.tm_wday;
              }
#else
              auto nm = detail::weekday_names();
              auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
              if (!is.fail()) {
                trial_wd = i % 7;
              }
#endif
            }
            else
              read(is, CharT{'%'}, width, modified, *fmt);
          }
          else { // *fmt == 'u' || *fmt == 'w'
#if !ONLY_C_LOCALE
            if (modified == CharT {})
#else
            if (modified != CharT {'E'})
#endif
            {
              read(is, ru{trial_wd, 1, width == -1 ?
                          1u : static_cast<unsigned>(width)});
              if (!is.fail()) {
                if (*fmt == 'u') {
                  if (!(1 <= trial_wd && trial_wd <= 7)) {
                    trial_wd = not_a_weekday;
                    is.setstate(ios::failbit);
                  }
                  else if (trial_wd == 7) {
                    trial_wd = 0;
                  }
                }
                else { // *fmt == 'w'
                  if (!(0 <= trial_wd && trial_wd <= 6)) {
                    trial_wd = not_a_weekday;
                    is.setstate(ios::failbit);
                  }
                }
              }
            }
#if !ONLY_C_LOCALE
            else if (modified == CharT {'O'}) {
              ios::iostate err = ios::goodbit;
              f.get(is, nullptr, is, err, &tm, command, fmt + 1);
              is.setstate(err);
              if (!is.fail()) {
                trial_wd = tm.tm_wday;
              }
            }
#endif
            else
              read(is, CharT{'%'}, width, modified, *fmt);
          }
          if (trial_wd != not_a_weekday) {
            checked_set(wd, trial_wd, not_a_weekday, is);
          }
        }
        else { // !command
          read(is, *fmt);
        }
        command = nullptr;
        width = -1;
        modified = CharT{};
        break;
      case 'b':
      case 'B':
      case 'h':
        if (command) {
          if (modified == CharT{}) {
            int ttm = not_a_month;
#if !ONLY_C_LOCALE
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              ttm = tm.tm_mon + 1;
            }
            is.setstate(err);
#else
            auto nm = detail::month_names();
            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
            if (!is.fail()) {
              ttm = i % 12 + 1;
            }
#endif
            checked_set(m, ttm, not_a_month, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'c':
        if (command) {
          if (modified != CharT{'O'}) {
#if !ONLY_C_LOCALE
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(Y, tm.tm_year + 1900, not_a_year, is);
              checked_set(m, tm.tm_mon + 1, not_a_month, is);
              checked_set(d, tm.tm_mday, not_a_day, is);
              checked_set(H, tm.tm_hour, not_a_hour, is);
              checked_set(M, tm.tm_min, not_a_minute, is);
              checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
                          not_a_second, is);
            }
            is.setstate(err);
#else
            // "%a %b %e %T %Y"
            auto nm = detail::weekday_names();
            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
            checked_set(wd, static_cast<int>(i % 7), not_a_weekday, is);
            ws(is);
            nm = detail::month_names();
            i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
            checked_set(m, static_cast<int>(i % 12 + 1), not_a_month, is);
            ws(is);
            int td = not_a_day;
            read(is, rs{td, 1, 2});
            checked_set(d, td, not_a_day, is);
            ws(is);
            using dfs = detail::decimal_format_seconds<Duration>;
            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
            int tH;
            int tM;
            long double S;
            read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
                 CharT{':'}, rld{S, 1, w});
            checked_set(H, tH, not_a_hour, is);
            checked_set(M, tM, not_a_minute, is);
            checked_set(s, round<Duration>(duration<long double> {S}),
                        not_a_second, is);
            ws(is);
            int tY = not_a_year;
            read(is, rs{tY, 1, 4u});
            checked_set(Y, tY, not_a_year, is);
#endif
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'x':
        if (command) {
          if (modified != CharT{'O'}) {
#if !ONLY_C_LOCALE
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(Y, tm.tm_year + 1900, not_a_year, is);
              checked_set(m, tm.tm_mon + 1, not_a_month, is);
              checked_set(d, tm.tm_mday, not_a_day, is);
            }
            is.setstate(err);
#else
            // "%m/%d/%y"
            int ty = not_a_2digit_year;
            int tm = not_a_month;
            int td = not_a_day;
            read(is, ru{tm, 1, 2}, CharT{'/'}, ru{td, 1, 2}, CharT{'/'},
                 rs{ty, 1, 2});
            checked_set(y, ty, not_a_2digit_year, is);
            checked_set(m, tm, not_a_month, is);
            checked_set(d, td, not_a_day, is);
#endif
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'X':
        if (command) {
          if (modified != CharT{'O'}) {
#if !ONLY_C_LOCALE
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(H, tm.tm_hour, not_a_hour, is);
              checked_set(M, tm.tm_min, not_a_minute, is);
              checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
                          not_a_second, is);
            }
            is.setstate(err);
#else
            // "%T"
            using dfs = detail::decimal_format_seconds<Duration>;
            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
            int tH = not_a_hour;
            int tM = not_a_minute;
            long double S;
            read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
                 CharT{':'}, rld{S, 1, w});
            checked_set(H, tH, not_a_hour, is);
            checked_set(M, tM, not_a_minute, is);
            checked_set(s, round<Duration>(duration<long double> {S}),
                        not_a_second, is);
#endif
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'C':
        if (command) {
          int tC = not_a_century;
#if !ONLY_C_LOCALE
          if (modified == CharT {}) {
#endif
            read(is, rs {tC, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
#if !ONLY_C_LOCALE
          }
          else {
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              auto tY = tm.tm_year + 1900;
              tC = (tY >= 0 ? tY : tY - 99) / 100;
            }
            is.setstate(err);
          }
#endif
          checked_set(C, tC, not_a_century, is);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'D':
        if (command) {
          if (modified == CharT{}) {
            int tn = not_a_month;
            int td = not_a_day;
            int ty = not_a_2digit_year;
            read(is, ru{tn, 1, 2}, CharT{'\0'}, CharT{'/'}, CharT{'\0'},
                 ru{td, 1, 2}, CharT{'\0'}, CharT{'/'}, CharT{'\0'},
                 rs{ty, 1, 2});
            checked_set(y, ty, not_a_2digit_year, is);
            checked_set(m, tn, not_a_month, is);
            checked_set(d, td, not_a_day, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'F':
        if (command) {
          if (modified == CharT{}) {
            int tY = not_a_year;
            int tn = not_a_month;
            int td = not_a_day;
            read(is, rs{tY, 1, width == -1 ? 4u : static_cast<unsigned>(width)},
                 CharT{'-'}, ru{tn, 1, 2}, CharT{'-'}, ru{td, 1, 2});
            checked_set(Y, tY, not_a_year, is);
            checked_set(m, tn, not_a_month, is);
            checked_set(d, td, not_a_day, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'd':
      case 'e':
        if (command) {
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#else
          if (modified != CharT {'E'})
#endif
          {
            int td = not_a_day;
            read(is, rs{td, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(d, td, not_a_day, is);
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            command = nullptr;
            width = -1;
            modified = CharT{};
            if ((err & ios::failbit) == 0) {
              checked_set(d, tm.tm_mday, not_a_day, is);
            }
            is.setstate(err);
          }
#endif
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'H':
        if (command) {
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#else
          if (modified != CharT {'E'})
#endif
          {
            int tH = not_a_hour;
            read(is, ru{tH, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(H, tH, not_a_hour, is);
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(H, tm.tm_hour, not_a_hour, is);
            }
            is.setstate(err);
          }
#endif
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'I':
        if (command) {
          if (modified == CharT{}) {
            int tI = not_a_hour_12_value;
            // reads in an hour into I, but most be in [1, 12]
            read(is, rs{tI, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            if (!(1 <= tI && tI <= 12)) {
              is.setstate(ios::failbit);
            }
            checked_set(I, tI, not_a_hour_12_value, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'j':
        if (command) {
          if (modified == CharT{}) {
            int tj = not_a_doy;
            read(is, ru{tj, 1, width == -1 ? 3u : static_cast<unsigned>(width)});
            checked_set(j, tj, not_a_doy, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'M':
        if (command) {
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#else
          if (modified != CharT {'E'})
#endif
          {
            int tM = not_a_minute;
            read(is, ru{tM, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(M, tM, not_a_minute, is);
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(M, tm.tm_min, not_a_minute, is);
            }
            is.setstate(err);
          }
#endif
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'm':
        if (command) {
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#else
          if (modified != CharT {'E'})
#endif
          {
            int tn = not_a_month;
            read(is, rs{tn, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(m, tn, not_a_month, is);
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(m, tm.tm_mon + 1, not_a_month, is);
            }
            is.setstate(err);
          }
#endif
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'n':
      case 't':
        if (command) {
          if (modified == CharT{}) {
            // %n matches a single white space character
            // %t matches 0 or 1 white space characters
            auto ic = is.peek();
            if (Traits::eq_int_type(ic, Traits::eof())) {
              ios::iostate err = ios::eofbit;
              if (*fmt == 'n') {
                err |= ios::failbit;
              }
              is.setstate(err);
              break;
            }
            if (isspace(ic)) {
              (void)is.get();
            }
            else if (*fmt == 'n') {
              is.setstate(ios::failbit);
            }
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'p':
        if (command) {
          if (modified == CharT{}) {
            int tp = not_a_ampm;
#if !ONLY_C_LOCALE
            tm = std::tm {};
            tm.tm_hour = 1;
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            is.setstate(err);
            if (tm.tm_hour == 1) {
              tp = 0;
            }
            else if (tm.tm_hour == 13) {
              tp = 1;
            }
            else {
              is.setstate(err);
            }
#else
            auto nm = detail::ampm_names();
            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
            tp = i;
#endif
            checked_set(p, tp, not_a_ampm, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }

        break;
      case 'r':
        if (command) {
          if (modified == CharT{}) {
#if !ONLY_C_LOCALE
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(H, tm.tm_hour, not_a_hour, is);
              checked_set(M, tm.tm_min, not_a_hour, is);
              checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
                          not_a_second, is);
            }
            is.setstate(err);
#else
            // "%I:%M:%S %p"
            using dfs = detail::decimal_format_seconds<Duration>;
            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
            long double S;
            int tI = not_a_hour_12_value;
            int tM = not_a_minute;
            read(is, ru{tI, 1, 2}, CharT{':'}, ru{tM, 1, 2},
                 CharT{':'}, rld{S, 1, w});
            checked_set(I, tI, not_a_hour_12_value, is);
            checked_set(M, tM, not_a_minute, is);
            checked_set(s, round<Duration>(duration<long double> {S}),
                        not_a_second, is);
            ws(is);
            auto nm = detail::ampm_names();
            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
            checked_set(p, static_cast<int>(i), not_a_ampm, is);
#endif
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'R':
        if (command) {
          if (modified == CharT{}) {
            int tH = not_a_hour;
            int tM = not_a_minute;
            read(is, ru{tH, 1, 2}, CharT{'\0'}, CharT{':'}, CharT{'\0'},
                 ru{tM, 1, 2}, CharT{'\0'});
            checked_set(H, tH, not_a_hour, is);
            checked_set(M, tM, not_a_minute, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'S':
        if (command) {
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#else
          if (modified != CharT {'E'})
#endif
          {
            using dfs = detail::decimal_format_seconds<Duration>;
            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
            long double S;
            read(is, rld{S, 1, width == -1 ? w : static_cast<unsigned>(width)});
            checked_set(s, round<Duration>(duration<long double> {S}),
                        not_a_second, is);
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'O'}) {
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0)
              checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
                          not_a_second, is);
            is.setstate(err);
          }
#endif
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'T':
        if (command) {
          if (modified == CharT{}) {
            using dfs = detail::decimal_format_seconds<Duration>;
            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
            int tH = not_a_hour;
            int tM = not_a_minute;
            long double S;
            read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
                 CharT{':'}, rld{S, 1, w});
            checked_set(H, tH, not_a_hour, is);
            checked_set(M, tM, not_a_minute, is);
            checked_set(s, round<Duration>(duration<long double> {S}),
                        not_a_second, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'Y':
        if (command) {
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#else
          if (modified != CharT {'O'})
#endif
          {
            int tY = not_a_year;
            read(is, rs{tY, 1, width == -1 ? 4u : static_cast<unsigned>(width)});
            checked_set(Y, tY, not_a_year, is);
          }
#if !ONLY_C_LOCALE
          else if (modified == CharT {'E'}) {
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(Y, tm.tm_year + 1900, not_a_year, is);
            }
            is.setstate(err);
          }
#endif
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'y':
        if (command) {
#if !ONLY_C_LOCALE
          if (modified == CharT {})
#endif
          {
            int ty = not_a_2digit_year;
            read(is, ru{ty, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(y, ty, not_a_2digit_year, is);
          }
#if !ONLY_C_LOCALE
          else {
            ios::iostate err = ios::goodbit;
            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
            if ((err & ios::failbit) == 0) {
              checked_set(Y, tm.tm_year + 1900, not_a_year, is);
            }
            is.setstate(err);
          }
#endif
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'g':
        if (command) {
          if (modified == CharT{}) {
            int tg = not_a_2digit_year;
            read(is, ru{tg, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(g, tg, not_a_2digit_year, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'G':
        if (command) {
          if (modified == CharT{}) {
            int tG = not_a_year;
            read(is, rs{tG, 1, width == -1 ? 4u : static_cast<unsigned>(width)});
            checked_set(G, tG, not_a_year, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'U':
        if (command) {
          if (modified == CharT{}) {
            int tU = not_a_week_num;
            read(is, ru{tU, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(U, tU, not_a_week_num, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'V':
        if (command) {
          if (modified == CharT{}) {
            int tV = not_a_week_num;
            read(is, ru{tV, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(V, tV, not_a_week_num, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'W':
        if (command) {
          if (modified == CharT{}) {
            int tW = not_a_week_num;
            read(is, ru{tW, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
            checked_set(W, tW, not_a_week_num, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'E':
      case 'O':
        if (command) {
          if (modified == CharT{}) {
            modified = *fmt;
          }
          else {
            read(is, CharT{'%'}, width, modified, *fmt);
            command = nullptr;
            width = -1;
            modified = CharT{};
          }
        }
        else {
          read(is, *fmt);
        }
        break;
      case '%':
        if (command) {
          if (modified == CharT{})
            read(is, *fmt);
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          command = fmt;
        }
        break;
      case 'z':
        if (command) {
          int tH, tM;
          minutes toff = not_a_offset;
          bool neg = false;
          auto ic = is.peek();
          if (!Traits::eq_int_type(ic, Traits::eof())) {
            auto c = static_cast<char>(Traits::to_char_type(ic));
            if (c == '-') {
              neg = true;
            }
          }
          if (modified == CharT{}) {
            read(is, rs{tH, 2, 2});
            if (!is.fail())
              toff = hours{std::abs(tH)};
            if (is.good()) {
              ic = is.peek();
              if (!Traits::eq_int_type(ic, Traits::eof())) {
                auto c = static_cast<char>(Traits::to_char_type(ic));
                if ('0' <= c && c <= '9') {
                  read(is, ru{tM, 2, 2});
                  if (!is.fail())
                    toff += minutes{tM};
                }
              }
            }
          }
          else {
            read(is, rs{tH, 1, 2});
            if (!is.fail())
              toff = hours{std::abs(tH)};
            if (is.good()) {
              ic = is.peek();
              if (!Traits::eq_int_type(ic, Traits::eof())) {
                auto c = static_cast<char>(Traits::to_char_type(ic));
                if (c == ':') {
                  (void)is.get();
                  read(is, ru{tM, 2, 2});
                  if (!is.fail())
                    toff += minutes{tM};
                }
              }
            }
          }
          if (neg) {
            toff = -toff;
          }
          checked_set(temp_offset, toff, not_a_offset, is);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      case 'Z':
        if (command) {
          if (modified == CharT{}) {
            std::basic_string<CharT, Traits, Alloc> buf;
            while (is.rdstate() == std::ios::goodbit) {
              auto i = is.rdbuf()->sgetc();
              if (Traits::eq_int_type(i, Traits::eof())) {
                is.setstate(ios::eofbit);
                break;
              }
              auto wc = Traits::to_char_type(i);
              auto c = static_cast<char>(wc);
              // is c a valid time zone name or abbreviation character?
              if (!(CharT{1} < wc && wc < CharT{127}) || !(isalnum(c) ||
                  c == '_' || c == '/' || c == '-' || c == '+'))
                break;
              buf.push_back(c);
              is.rdbuf()->sbumpc();
            }
            if (buf.empty()) {
              is.setstate(ios::failbit);
            }
            checked_set(temp_abbrev, buf, {}, is);
          }
          else
            read(is, CharT{'%'}, width, modified, *fmt);
          command = nullptr;
          width = -1;
          modified = CharT{};
        }
        else {
          read(is, *fmt);
        }
        break;
      default:
        if (command) {
          if (width == -1 && modified == CharT{} && '0' <= *fmt && *fmt <= '9') {
            width = static_cast<char>(*fmt) - '0';
            while ('0' <= fmt[1] && fmt[1] <= '9') {
              width = 10 * width + static_cast<char>(*++fmt) - '0';
            }
          }
          else {
            if (modified == CharT{})
              read(is, CharT{'%'}, width, *fmt);
            else
              read(is, CharT{'%'}, width, modified, *fmt);
            command = nullptr;
            width = -1;
            modified = CharT{};
          }
        }
        else { // !command
          if (isspace(static_cast<unsigned char>(*fmt))) {
            // space matches 0 or more white space characters
            if (is.good()) {
              ws(is);
            }
          }
          else {
            read(is, *fmt);
          }
        }
        break;
      }
    }
    // is.fail() || *fmt == CharT{}
    if (is.rdstate() == ios::goodbit && command) {
      if (modified == CharT{})
        read(is, CharT{'%'}, width);
      else
        read(is, CharT{'%'}, width, modified);
    }
    if (!is.fail()) {
      if (y != not_a_2digit_year) {
        // Convert y and an optional C to Y
        if (!(0 <= y && y <= 99)) {
          goto broken;
        }
        if (C == not_a_century) {
          if (Y == not_a_year) {
            if (y >= 69) {
              C = 19;
            }
            else {
              C = 20;
            }
          }
          else {
            C = (Y >= 0 ? Y : Y - 100) / 100;
          }
        }
        int tY;
        if (C >= 0) {
          tY = 100 * C + y;
        }
        else {
          tY = 100 * (C + 1) - (y == 0 ? 100 : y);
        }
        if (Y != not_a_year && Y != tY) {
          goto broken;
        }
        Y = tY;
      }
      if (g != not_a_2digit_year) {
        // Convert g and an optional C to G
        if (!(0 <= g && g <= 99)) {
          goto broken;
        }
        if (C == not_a_century) {
          if (G == not_a_year) {
            if (g >= 69) {
              C = 19;
            }
            else {
              C = 20;
            }
          }
          else {
            C = (G >= 0 ? G : G - 100) / 100;
          }
        }
        int tG;
        if (C >= 0) {
          tG = 100 * C + g;
        }
        else {
          tG = 100 * (C + 1) - (g == 0 ? 100 : g);
        }
        if (G != not_a_year && G != tG) {
          goto broken;
        }
        G = tG;
      }
      if (Y < static_cast<int>(year::min()) || Y > static_cast<int>(year::max())) {
        Y = not_a_year;
      }
      bool computed = false;
      if (G != not_a_year && V != not_a_week_num && wd != not_a_weekday) {
        year_month_day ymd_trial = sys_days(year{G - 1} / December / Thursday[last]) +
                                   (Monday - Thursday) + weeks{V - 1} +
                                   (weekday{static_cast<unsigned>(wd)} -Monday);
        if (Y == not_a_year) {
          Y = static_cast<int>(ymd_trial.year());
        }
        else if (year{Y} != ymd_trial.year())
          goto broken;
        if (m == not_a_month) {
          m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
        }
        else if (month(static_cast<unsigned>(m)) != ymd_trial.month()) {
          goto broken;
        }
        if (d == not_a_day) {
          d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
        }
        else if (day(static_cast<unsigned>(d)) != ymd_trial.day()) {
          goto broken;
        }
        computed = true;
      }
      if (Y != not_a_year && U != not_a_week_num && wd != not_a_weekday) {
        year_month_day ymd_trial = sys_days(year{Y} / January / Sunday[1]) +
                                   weeks{U - 1} +
                                   (weekday{static_cast<unsigned>(wd)} - Sunday);
        if (Y == not_a_year) {
          Y = static_cast<int>(ymd_trial.year());
        }
        else if (year{Y} != ymd_trial.year())
          goto broken;
        if (m == not_a_month) {
          m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
        }
        else if (month(static_cast<unsigned>(m)) != ymd_trial.month()) {
          goto broken;
        }
        if (d == not_a_day) {
          d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
        }
        else if (day(static_cast<unsigned>(d)) != ymd_trial.day()) {
          goto broken;
        }
        computed = true;
      }
      if (Y != not_a_year && W != not_a_week_num && wd != not_a_weekday) {
        year_month_day ymd_trial = sys_days(year{Y} / January / Monday[1]) +
                                   weeks{W - 1} +
                                   (weekday{static_cast<unsigned>(wd)} - Monday);
        if (Y == not_a_year) {
          Y = static_cast<int>(ymd_trial.year());
        }
        else if (year{Y} != ymd_trial.year())
          goto broken;
        if (m == not_a_month) {
          m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
        }
        else if (month(static_cast<unsigned>(m)) != ymd_trial.month()) {
          goto broken;
        }
        if (d == not_a_day) {
          d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
        }
        else if (day(static_cast<unsigned>(d)) != ymd_trial.day()) {
          goto broken;
        }
        computed = true;
      }
      if (j != not_a_doy && Y != not_a_year) {
        auto ymd_trial = year_month_day{local_days(year{Y} / 1 / 1) + days{j - 1}};
        if (m == 0) {
          m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
        }
        else if (month(static_cast<unsigned>(m)) != ymd_trial.month()) {
          goto broken;
        }
        if (d == 0) {
          d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
        }
        else if (day(static_cast<unsigned>(d)) != ymd_trial.day()) {
          goto broken;
        }
        j = not_a_doy;
      }
      auto ymd = year{Y} / m / d;
      if (ymd.ok()) {
        if (wd == not_a_weekday) {
          wd = static_cast<int>((weekday(sys_days(ymd)) - Sunday).count());
        }
        else if (wd != static_cast<int>((weekday(sys_days(ymd)) - Sunday).count())) {
          goto broken;
        }
        if (!computed) {
          if (G != not_a_year || V != not_a_week_num) {
            sys_days sd = ymd;
            auto G_trial = year_month_day{sd + days{3}}.year();
            auto start = sys_days((G_trial - years{1}) / December / Thursday[last]) +
                         (Monday - Thursday);
            if (sd < start) {
              --G_trial;
              if (V != not_a_week_num)
                start = sys_days((G_trial - years{1}) / December / Thursday[last])
                        + (Monday - Thursday);
            }
            if (G != not_a_year && G != static_cast<int>(G_trial)) {
              goto broken;
            }
            if (V != not_a_week_num) {
              auto V_trial = duration_cast<weeks>(sd - start).count() + 1;
              if (V != V_trial) {
                goto broken;
              }
            }
          }
          if (U != not_a_week_num) {
            auto start = sys_days(Sunday[1] / January / ymd.year());
            auto U_trial = floor<weeks>(sys_days(ymd) - start).count() + 1;
            if (U != U_trial) {
              goto broken;
            }
          }
          if (W != not_a_week_num) {
            auto start = sys_days(Monday[1] / January / ymd.year());
            auto W_trial = floor<weeks>(sys_days(ymd) - start).count() + 1;
            if (W != W_trial) {
              goto broken;
            }
          }
        }
      }
      fds.ymd = ymd;
      if (I != not_a_hour_12_value) {
        if (!(1 <= I && I <= 12)) {
          goto broken;
        }
        if (p != not_a_ampm) {
          // p is in [0, 1] == [AM, PM]
          // Store trial H in I
          if (I == 12) {
            --p;
          }
          I += p * 12;
          // Either set H from I or make sure H and I are consistent
          if (H == not_a_hour) {
            H = I;
          }
          else if (I != H) {
            goto broken;
          }
        }
        else { // p == not_a_ampm
          // if H, make sure H and I could be consistent
          if (H != not_a_hour) {
            if (I == 12) {
              if (H != 0 && H != 12) {
                goto broken;
              }
            }
            else if (!(I == H || I == H + 12)) {
              goto broken;
            }
          }
        }
      }
      if (H != not_a_hour) {
        fds.has_tod = true;
        fds.tod = hh_mm_ss<Duration> {hours{H}};
      }
      if (M != not_a_minute) {
        fds.has_tod = true;
        fds.tod.m_ = minutes{M};
      }
      if (s != not_a_second) {
        fds.has_tod = true;
        fds.tod.s_ = detail::decimal_format_seconds<Duration> {s};
      }
      if (j != not_a_doy) {
        fds.has_tod = true;
        fds.tod.h_ += hours{days{j}};
      }
      if (wd != not_a_weekday)
        fds.wd = weekday{static_cast<unsigned>(wd)};
      if (abbrev != nullptr) {
        *abbrev = std::move(temp_abbrev);
      }
      if (offset != nullptr && temp_offset != not_a_offset) {
        *offset = temp_offset;
      }
    }
    return is;
  }
broken:
  is.setstate(ios::failbit);
  return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, year &y,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{};
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.ymd.year().ok()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    y = fds.ymd.year();
  }
  return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, month &m,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{};
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.ymd.month().ok()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    m = fds.ymd.month();
  }
  return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, day &d,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{};
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.ymd.day().ok()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    d = fds.ymd.day();
  }
  return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            weekday &wd,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{};
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.wd.ok()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    wd = fds.wd;
  }
  return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            year_month &ym,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{};
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.ymd.month().ok()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    ym = fds.ymd.year() / fds.ymd.month();
  }
  return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            month_day &md,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{};
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.ymd.month().ok() || !fds.ymd.day().ok()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    md = fds.ymd.month() / fds.ymd.day();
  }
  return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            year_month_day &ymd, std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = std::chrono::seconds;
  fields<CT> fds{};
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.ymd.ok()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    ymd = fds.ymd;
  }
  return is;
}

template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            sys_time<Duration> &tp, std::basic_string<CharT, Traits, Alloc> *abbrev =
            nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
  std::chrono::minutes offset_local{};
  auto offptr = offset ? offset : &offset_local;
  fields<CT> fds{};
  fds.has_tod = true;
  from_stream(is, fmt, fds, abbrev, offptr);
  if (!fds.ymd.ok() || !fds.tod.in_conventional_range()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    tp = round<Duration>(sys_days(fds.ymd) - *offptr + fds.tod.to_duration());
  }
  return is;
}

template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            local_time<Duration> &tp,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
  fields<CT> fds{};
  fds.has_tod = true;
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.ymd.ok() || !fds.tod.in_conventional_range()) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail())
    tp = round<Duration>(local_seconds{local_days(fds.ymd)} +
                         fds.tod.to_duration());
  return is;
}

template <class Rep, class Period, class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            std::chrono::duration<Rep, Period> &d,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr)
{
  using Duration = std::chrono::duration<Rep, Period>;
  using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
  fields<CT> fds{};
  from_stream(is, fmt, fds, abbrev, offset);
  if (!fds.has_tod) {
    is.setstate(std::ios::failbit);
  }
  if (!is.fail()) {
    d = std::chrono::duration_cast<Duration>(fds.tod.to_duration());
  }
  return is;
}

template <class Parsable, class CharT, class Traits = std::char_traits<CharT>,
          class Alloc = std::allocator<CharT>>
struct parse_manip {
  const std::basic_string<CharT, Traits, Alloc> format_;
  Parsable                                     &tp_;
  std::basic_string<CharT, Traits, Alloc>      *abbrev_;
  std::chrono::minutes                         *offset_;

public:
  parse_manip(std::basic_string<CharT, Traits, Alloc> format, Parsable &tp,
              std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
              std::chrono::minutes *offset = nullptr)
    : format_(std::move(format))
    , tp_(tp)
    , abbrev_(abbrev)
    , offset_(offset)
  {}

};

template <class Parsable, class CharT, class Traits, class Alloc>
std::basic_istream<CharT, Traits> &
operator>>(std::basic_istream<CharT, Traits> &is,
           const parse_manip<Parsable, CharT, Traits, Alloc> &x)
{
  return from_stream(is, x.format_.c_str(), x.tp_, x.abbrev_, x.offset_);
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline
auto
parse(const std::basic_string<CharT, Traits, Alloc> &format, Parsable &tp)
-> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
                        format.c_str(), tp),
            parse_manip<Parsable, CharT, Traits, Alloc>
{
  format, tp
})
{
  return {format, tp};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline
auto
parse(const std::basic_string<CharT, Traits, Alloc> &format, Parsable &tp,
      std::basic_string<CharT, Traits, Alloc> &abbrev)
-> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
                        format.c_str(), tp, &abbrev),
            parse_manip<Parsable, CharT, Traits, Alloc>
{
  format, tp, &abbrev
})
{
  return {format, tp, &abbrev};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline
auto
parse(const std::basic_string<CharT, Traits, Alloc> &format, Parsable &tp,
      std::chrono::minutes &offset)
-> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
                        format.c_str(), tp,
                        std::declval<std::basic_string<CharT, Traits, Alloc>*>(),
                        &offset),
            parse_manip<Parsable, CharT, Traits, Alloc>
{
  format, tp, nullptr, &offset
})
{
  return {format, tp, nullptr, &offset};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline
auto
parse(const std::basic_string<CharT, Traits, Alloc> &format, Parsable &tp,
      std::basic_string<CharT, Traits, Alloc> &abbrev, std::chrono::minutes &offset)
-> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
                        format.c_str(), tp, &abbrev, &offset),
            parse_manip<Parsable, CharT, Traits, Alloc>
{
  format, tp, &abbrev, &offset
})
{
  return {format, tp, &abbrev, &offset};
}

// const CharT* formats

template <class Parsable, class CharT>
inline
auto
parse(const CharT *format, Parsable &tp)
-> decltype(from_stream(std::declval<std::basic_istream<CharT>&>(), format, tp),
            parse_manip<Parsable, CharT>
{
  format, tp
})
{
  return {format, tp};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline
auto
parse(const CharT *format, Parsable &tp,
      std::basic_string<CharT, Traits, Alloc> &abbrev)
-> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
                        format,
                        tp, &abbrev),
            parse_manip<Parsable, CharT, Traits, Alloc>
{
  format, tp, &abbrev
})
{
  return {format, tp, &abbrev};
}

template <class Parsable, class CharT>
inline
auto
parse(const CharT *format, Parsable &tp, std::chrono::minutes &offset)
-> decltype(from_stream(std::declval<std::basic_istream<CharT>&>(), format,
                        tp, std::declval<std::basic_string<CharT>*>(), &offset),
            parse_manip<Parsable, CharT>
{
  format, tp, nullptr, &offset
})
{
  return {format, tp, nullptr, &offset};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline
auto
parse(const CharT *format, Parsable &tp,
      std::basic_string<CharT, Traits, Alloc> &abbrev, std::chrono::minutes &offset)
-> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
                        format,
                        tp, &abbrev, &offset),
            parse_manip<Parsable, CharT, Traits, Alloc>
{
  format, tp, &abbrev, &offset
})
{
  return {format, tp, &abbrev, &offset};
}

// duration streaming

template <class CharT, class Traits, class Rep, class Period>
inline
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const std::chrono::duration<Rep, Period> &d)
{
  return os << detail::make_string<CharT, Traits>::from(d.count()) +
             detail::get_units<CharT>(typename Period::type{});
}

}  // namespace date

#ifdef _MSC_VER
#   pragma warning(pop)
#endif

#ifdef __GNUC__
# pragma GCC diagnostic pop
#endif

#endif  // DATE_H