// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_CHRONO
#define _LIBCPP_CHRONO

// clang-format off

/*
    chrono synopsis

#include <compare> // C++20

namespace std
{
namespace chrono
{

template <class ToDuration, class Rep, class Period>
constexpr
ToDuration
duration_cast(const duration<Rep, Period>& fd);

template <class Rep> struct treat_as_floating_point : is_floating_point<Rep> {};

template <class Rep> inline constexpr bool treat_as_floating_point_v
    = treat_as_floating_point<Rep>::value;                       // C++17

template <class Rep>
struct duration_values
{
public:
    static constexpr Rep zero(); // noexcept in C++20
    static constexpr Rep max();  // noexcept in C++20
    static constexpr Rep min();  // noexcept in C++20
};

// duration

template <class Rep, class Period = ratio<1>>
class duration
{
    static_assert(!__is_duration<Rep>::value, "A duration representation can not be a duration");
    static_assert(__is_ratio<Period>::value, "Second template parameter of duration must be a std::ratio");
    static_assert(Period::num > 0, "duration period must be positive");
public:
    typedef Rep rep;
    typedef typename _Period::type period;

    constexpr duration() = default;
    template <class Rep2>
        constexpr explicit duration(const Rep2& r,
            typename enable_if
            <
               is_convertible<const Rep2&, rep>::value &&
               (treat_as_floating_point<rep>::value ||
               !treat_as_floating_point<rep>::value && !treat_as_floating_point<Rep2>::value)
            >::type* = 0);

    // conversions
    template <class Rep2, class Period2>
        constexpr duration(const duration<Rep2, Period2>& d,
            typename enable_if
            <
                treat_as_floating_point<rep>::value ||
                ratio_divide<Period2, period>::type::den == 1
            >::type* = 0);

    // observer

    constexpr rep count() const;

    // arithmetic

    constexpr common_type<duration>::type  operator+() const;
    constexpr common_type<duration>::type  operator-() const;
    constexpr duration& operator++();    // constexpr in C++17
    constexpr duration  operator++(int); // constexpr in C++17
    constexpr duration& operator--();    // constexpr in C++17
    constexpr duration  operator--(int); // constexpr in C++17

    constexpr duration& operator+=(const duration& d);  // constexpr in C++17
    constexpr duration& operator-=(const duration& d);  // constexpr in C++17

    duration& operator*=(const rep& rhs);       // constexpr in C++17
    duration& operator/=(const rep& rhs);       // constexpr in C++17
    duration& operator%=(const rep& rhs);       // constexpr in C++17
    duration& operator%=(const duration& rhs);  // constexpr in C++17

    // special values

    static constexpr duration zero(); // noexcept in C++20
    static constexpr duration min();  // noexcept in C++20
    static constexpr duration max();  // noexcept in C++20
};

typedef duration<long long,         nano> nanoseconds;
typedef duration<long long,        micro> microseconds;
typedef duration<long long,        milli> milliseconds;
typedef duration<long long              > seconds;
typedef duration<     long, ratio<  60> > minutes;
typedef duration<     long, ratio<3600> > hours;

template <class Clock, class Duration = typename Clock::duration>
class time_point
{
public:
    typedef Clock                     clock;
    typedef Duration                  duration;
    typedef typename duration::rep    rep;
    typedef typename duration::period period;
private:
    duration d_;  // exposition only

public:
    time_point();  // has value "epoch" // constexpr in C++14
    explicit time_point(const duration& d);  // same as time_point() + d // constexpr in C++14

    // conversions
    template <class Duration2>
       time_point(const time_point<clock, Duration2>& t); // constexpr in C++14

    // observer

    duration time_since_epoch() const; // constexpr in C++14

    // arithmetic

    constexpr time_point& operator++();    // C++20
    constexpr time_point  operator++(int); // C++20
    constexpr time_point& operator--();    // C++20
    constexpr time_point  operator--(int); // C++20

    time_point& operator+=(const duration& d); // constexpr in C++17
    time_point& operator-=(const duration& d); // constexpr in C++17

    // special values

    static constexpr time_point min();  // noexcept in C++20
    static constexpr time_point max();  // noexcept in C++20
};

} // chrono

// common_type traits
template <class Rep1, class Period1, class Rep2, class Period2>
  struct common_type<chrono::duration<Rep1, Period1>, chrono::duration<Rep2, Period2>>;

template <class Clock, class Duration1, class Duration2>
  struct common_type<chrono::time_point<Clock, Duration1>, chrono::time_point<Clock, Duration2>>;

namespace chrono {

// duration arithmetic
template <class Rep1, class Period1, class Rep2, class Period2>
  constexpr
  typename common_type<duration<Rep1, Period1>, duration<Rep2, Period2>>::type
  operator+(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
  constexpr
  typename common_type<duration<Rep1, Period1>, duration<Rep2, Period2>>::type
  operator-(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period, class Rep2>
  constexpr
  duration<typename common_type<Rep1, Rep2>::type, Period>
  operator*(const duration<Rep1, Period>& d, const Rep2& s);
template <class Rep1, class Period, class Rep2>
  constexpr
  duration<typename common_type<Rep1, Rep2>::type, Period>
  operator*(const Rep1& s, const duration<Rep2, Period>& d);
template <class Rep1, class Period, class Rep2>
  constexpr
  duration<typename common_type<Rep1, Rep2>::type, Period>
  operator/(const duration<Rep1, Period>& d, const Rep2& s);
template <class Rep1, class Period1, class Rep2, class Period2>
  constexpr
  typename common_type<Rep1, Rep2>::type
  operator/(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);

// duration comparisons
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator==(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator!=(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs); // removed in C++20
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator< (const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator<=(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator> (const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator>=(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template<class Rep1, class Period1, class Rep2, class Period2>
  requires three_way_comparable<typename CT::rep>
  constexpr auto operator<=>(const duration<Rep1, Period1>& lhs,
                             const duration<Rep2, Period2>& rhs);                           // since C++20

// duration_cast
template <class ToDuration, class Rep, class Period>
  ToDuration duration_cast(const duration<Rep, Period>& d);

template <class ToDuration, class Rep, class Period>
    constexpr ToDuration floor(const duration<Rep, Period>& d);    // C++17
template <class ToDuration, class Rep, class Period>
    constexpr ToDuration ceil(const duration<Rep, Period>& d);     // C++17
template <class ToDuration, class Rep, class Period>
    constexpr ToDuration round(const duration<Rep, Period>& d);    // C++17

// duration I/O
template<class charT, class traits, class Rep, class Period>       // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os,
               const duration<Rep, Period>& d);

// time_point arithmetic (all constexpr in C++14)
template <class Clock, class Duration1, class Rep2, class Period2>
  time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type>
  operator+(const time_point<Clock, Duration1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Clock, class Duration2>
  time_point<Clock, typename common_type<duration<Rep1, Period1>, Duration2>::type>
  operator+(const duration<Rep1, Period1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Rep2, class Period2>
  time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type>
  operator-(const time_point<Clock, Duration1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Clock, class Duration1, class Duration2>
  typename common_type<Duration1, Duration2>::type
  operator-(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);

// time_point comparisons (all constexpr in C++14)
template <class Clock, class Duration1, class Duration2>
   bool operator==(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator!=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs); // removed in C++20
template <class Clock, class Duration1, class Duration2>
   bool operator< (const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator<=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator> (const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator>=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template<class Clock, class Duration1,
         three_way_comparable_with<Duration1> Duration2>
  constexpr auto operator<=>(const time_point<Clock, Duration1>& lhs,
                             const time_point<Clock, Duration2>& rhs);                                // since C++20

// time_point_cast (constexpr in C++14)

template <class ToDuration, class Clock, class Duration>
  time_point<Clock, ToDuration> time_point_cast(const time_point<Clock, Duration>& t);

template <class ToDuration, class Clock, class Duration>
    constexpr time_point<Clock, ToDuration>
    floor(const time_point<Clock, Duration>& tp);                  // C++17

template <class ToDuration, class Clock, class Duration>
    constexpr time_point<Clock, ToDuration>
    ceil(const time_point<Clock, Duration>& tp);                   // C++17

template <class ToDuration, class Clock, class Duration>
    constexpr time_point<Clock, ToDuration>
    round(const time_point<Clock, Duration>& tp);                  // C++17

template <class Rep, class Period>
    constexpr duration<Rep, Period> abs(duration<Rep, Period> d);  // C++17

// Clocks

class system_clock
{
public:
    typedef microseconds                     duration;
    typedef duration::rep                    rep;
    typedef duration::period                 period;
    typedef chrono::time_point<system_clock> time_point;
    static const bool is_steady =            false; // constexpr in C++14

    static time_point now() noexcept;
    static time_t     to_time_t  (const time_point& __t) noexcept;
    static time_point from_time_t(time_t __t) noexcept;
};

template <class Duration>
  using sys_time  = time_point<system_clock, Duration>; // C++20
using sys_seconds = sys_time<seconds>;                  // C++20
using sys_days    = sys_time<days>;                     // C++20

template<class charT, class traits, class Duration>     // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const sys_time<Duration>& tp);

template<class charT, class traits>                    // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const sys_days& dp);

// [time.clock.utc], class utc_clock
class utc_clock {                                      // C++20
public:
    using rep                       = a signed arithmetic type;
    using period                    = ratio<unspecified, unspecified>;
    using duration                  = chrono::duration<rep, period>;
    using time_point                = chrono::time_point<utc_clock>;
    static constexpr bool is_steady = unspecified;

    static time_point now();

    template<class Duration>
      static sys_time<common_type_t<Duration, seconds>>
        to_sys(const utc_time<Duration>& t);
    template<class Duration>
      static utc_time<common_type_t<Duration, seconds>>
        from_sys(const sys_time<Duration>& t);
};

template<class Duration>
using utc_time  = time_point<utc_clock, Duration>;      // C++20
using utc_seconds = utc_time<seconds>;                  // C++20

template<class charT, class traits, class Duration>     // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const utc_time<Duration>& t);

struct leap_second_info {                               // C++20
  bool    is_leap_second;
  seconds elapsed;
};

template<class Duration>                                // C++20
  leap_second_info get_leap_second_info(const utc_time<Duration>& ut);


// [time.clock.tai], class tai_clock
class tai_clock {                                      // C++20
public:
    using rep                       = a signed arithmetic type;
    using period                    = ratio<unspecified, unspecified>;
    using duration                  = chrono::duration<rep, period>;
    using time_point                = chrono::time_point<tai_clock>;
    static constexpr bool is_steady = unspecified;

    static time_point now();

    template<class Duration>
      static utc_time<common_type_t<Duration, seconds>>
        to_utc(const tai_time<Duration>& t);
    template<class Duration>
      static tai_time<common_type_t<Duration, seconds>>
        from_utc(const utc_time<Duration>& t);
};

template<class Duration>
using tai_time  = time_point<tai_clock, Duration>;      // C++20
using tai_seconds = tai_time<seconds>;                  // C++20

template<class charT, class traits, class Duration>     // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const tai_time<Duration>& t);

// [time.clock.gps], class gps_clock
class gps_clock {                                      // C++20
public:
    using rep                       = a signed arithmetic type;
    using period                    = ratio<unspecified, unspecified>;
    using duration                  = chrono::duration<rep, period>;
    using time_point                = chrono::time_point<gps_clock>;
    static constexpr bool is_steady = unspecified;

    static time_point now();

    template<class Duration>
      static utc_time<common_type_t<Duration, seconds>>
        to_utc(const gps_time<Duration>& t);
    template<class Duration>
      static gps_time<common_type_t<Duration, seconds>>
        from_utc(const utc_time<Duration>& t);
};

template<class Duration>
using gps_time  = time_point<gps_clock, Duration>;      // C++20
using gps_seconds = gps_time<seconds>;                  // C++20

template<class charT, class traits, class Duration>     // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const gps_time<Duration>& t);

class file_clock                                        // C++20
{
public:
    typedef see-below                      rep;
    typedef nano                           period;
    typedef chrono::duration<rep, period>  duration;
    typedef chrono::time_point<file_clock> time_point;
    static constexpr bool is_steady =      false;

    static time_point now() noexcept;

    template<class Duration>
    static sys_time<see-below> to_sys(const file_time<Duration>&);

    template<class Duration>
    static file_time<see-below> from_sys(const sys_time<Duration>&);
};

template<class Duration>
  using file_time = time_point<file_clock, Duration>;   // C++20

template<class charT, class traits, class Duration>     // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const file_time<Duration>& tp);

class steady_clock
{
public:
    typedef nanoseconds                                   duration;
    typedef duration::rep                                 rep;
    typedef duration::period                              period;
    typedef chrono::time_point<steady_clock, duration>    time_point;
    static const bool is_steady =                         true; // constexpr in C++14

    static time_point now() noexcept;
};

typedef steady_clock high_resolution_clock;

// [time.clock.local] local time           // C++20
struct local_t {};
template<class Duration>
  using local_time  = time_point<local_t, Duration>;
using local_seconds = local_time<seconds>;
using local_days    = local_time<days>;

template<class charT, class traits, class Duration>     // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const local_time<Duration>& tp);

// [time.cal.last] class last_spec    // C++20
struct last_spec;

// [time.cal.day] class day          // C++20

class day;
constexpr bool operator==(const day& x, const day& y) noexcept;
constexpr strong_ordering operator<=>(const day& x, const day& y) noexcept;
constexpr day  operator+(const day&  x, const days& y) noexcept;
constexpr day  operator+(const days& x, const day&  y) noexcept;
constexpr day  operator-(const day&  x, const days& y) noexcept;
constexpr days operator-(const day&  x, const day&  y) noexcept;
template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const day& d);

// [time.cal.month] class month    // C++20
class month;
constexpr bool operator==(const month& x, const month& y) noexcept;
constexpr strong_ordering operator<=>(const month& x, const month& y) noexcept;

constexpr month  operator+(const month&  x, const months& y) noexcept;
constexpr month  operator+(const months& x,  const month& y) noexcept;
constexpr month  operator-(const month&  x, const months& y) noexcept;
constexpr months operator-(const month&  x,  const month& y) noexcept;
template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const month& m);

// [time.cal.year] class year    // C++20
class year;
constexpr bool operator==(const year& x, const year& y) noexcept;
constexpr strong_ordering operator<=>(const year& x, const year& y) noexcept;

constexpr year  operator+(const year&  x, const years& y) noexcept;
constexpr year  operator+(const years& x, const year&  y) noexcept;
constexpr year  operator-(const year&  x, const years& y) noexcept;
constexpr years operator-(const year&  x, const year&  y) noexcept;
template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const year& y);

// [time.cal.wd] class weekday    // C++20
class weekday;

constexpr bool operator==(const weekday& x, const weekday& y) noexcept;
constexpr weekday operator+(const weekday& x, const days&    y) noexcept;
constexpr weekday operator+(const days&    x, const weekday& y) noexcept;
constexpr weekday operator-(const weekday& x, const days&    y) noexcept;
constexpr days    operator-(const weekday& x, const weekday& y) noexcept;
template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const weekday& wd);

// [time.cal.wdidx] class weekday_indexed    // C++20

class weekday_indexed;
constexpr bool operator==(const weekday_indexed& x, const weekday_indexed& y) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const weekday_indexed& wdi);

// [time.cal.wdlast] class weekday_last    // C++20
class weekday_last;

constexpr bool operator==(const weekday_last& x, const weekday_last& y) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const weekday_last& wdl);

// [time.cal.md] class month_day    // C++20
class month_day;

constexpr bool operator==(const month_day& x, const month_day& y) noexcept;
constexpr strong_ordering operator<=>(const month_day& x, const month_day& y) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const month_day& md);

// [time.cal.mdlast] class month_day_last    // C++20
class month_day_last;

constexpr bool operator==(const month_day_last& x, const month_day_last& y) noexcept;
constexpr strong_ordering operator<=>(const month_day_last& x, const month_day_last& y) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const month_day_last& mdl);

// [time.cal.mwd] class month_weekday    // C++20
class month_weekday;

constexpr bool operator==(const month_weekday& x, const month_weekday& y) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const month_weekday& mwd);

// [time.cal.mwdlast] class month_weekday_last    // C++20
class month_weekday_last;

constexpr bool operator==(const month_weekday_last& x, const month_weekday_last& y) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const month_weekday_last& mwdl);


// [time.cal.ym] class year_month    // C++20
class year_month;

constexpr bool operator==(const year_month& x, const year_month& y) noexcept;
constexpr strong_ordering operator<=>(const year_month& x, const year_month& y) noexcept;

constexpr year_month operator+(const year_month& ym, const months& dm) noexcept;
constexpr year_month operator+(const months& dm, const year_month& ym) noexcept;
constexpr year_month operator-(const year_month& ym, const months& dm) noexcept;
constexpr months operator-(const year_month& x, const year_month& y) noexcept;
constexpr year_month operator+(const year_month& ym, const years& dy) noexcept;
constexpr year_month operator+(const years& dy, const year_month& ym) noexcept;
constexpr year_month operator-(const year_month& ym, const years& dy) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const year_month& ym);

// [time.cal.ymd] class year_month_day class    // C++20
year_month_day;

constexpr bool operator==(const year_month_day& x, const year_month_day& y) noexcept;
constexpr strong_ordering operator<=>(const year_month_day& x, const year_month_day& y) noexcept;

constexpr year_month_day operator+(const year_month_day& ymd, const months& dm) noexcept;
constexpr year_month_day operator+(const months& dm, const year_month_day& ymd) noexcept;
constexpr year_month_day operator+(const year_month_day& ymd, const years& dy) noexcept;
constexpr year_month_day operator+(const years& dy, const year_month_day& ymd) noexcept;
constexpr year_month_day operator-(const year_month_day& ymd, const months& dm) noexcept;
constexpr year_month_day operator-(const year_month_day& ymd, const years& dy) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const year_month_day& ymd);

// [time.cal.ymdlast] class year_month_day_last    // C++20
class year_month_day_last;

constexpr bool operator==(const year_month_day_last& x, const year_month_day_last& y) noexcept;
constexpr strong_ordering operator<=>(const year_month_day_last_day& x, const year_month_day_last_day& y) noexcept;

constexpr year_month_day_last
  operator+(const year_month_day_last& ymdl, const months& dm) noexcept;
constexpr year_month_day_last
  operator+(const months& dm, const year_month_day_last& ymdl) noexcept;
constexpr year_month_day_last
  operator+(const year_month_day_last& ymdl, const years& dy) noexcept;
constexpr year_month_day_last
  operator+(const years& dy, const year_month_day_last& ymdl) noexcept;
constexpr year_month_day_last
  operator-(const year_month_day_last& ymdl, const months& dm) noexcept;
constexpr year_month_day_last
  operator-(const year_month_day_last& ymdl, const years& dy) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const year_month_day_last& ymdl);

// [time.cal.ymwd] class year_month_weekday    // C++20
class year_month_weekday;

constexpr bool operator==(const year_month_weekday& x,
                          const year_month_weekday& y) noexcept;

constexpr year_month_weekday
  operator+(const year_month_weekday& ymwd, const months& dm) noexcept;
constexpr year_month_weekday
  operator+(const months& dm, const year_month_weekday& ymwd) noexcept;
constexpr year_month_weekday
  operator+(const year_month_weekday& ymwd, const years& dy) noexcept;
constexpr year_month_weekday
  operator+(const years& dy, const year_month_weekday& ymwd) noexcept;
constexpr year_month_weekday
  operator-(const year_month_weekday& ymwd, const months& dm) noexcept;
constexpr year_month_weekday
  operator-(const year_month_weekday& ymwd, const years& dy) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const year_month_weekday& ymwd);

// [time.cal.ymwdlast] class year_month_weekday_last    // C++20
class year_month_weekday_last;

constexpr bool operator==(const year_month_weekday_last& x,
                          const year_month_weekday_last& y) noexcept;
constexpr year_month_weekday_last
  operator+(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
constexpr year_month_weekday_last
  operator+(const months& dm, const year_month_weekday_last& ymwdl) noexcept;
constexpr year_month_weekday_last
  operator+(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
constexpr year_month_weekday_last
  operator+(const years& dy, const year_month_weekday_last& ymwdl) noexcept;
constexpr year_month_weekday_last
  operator-(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
constexpr year_month_weekday_last
  operator-(const year_month_weekday_last& ymwdl, const years& dy) noexcept;

template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const year_month_weekday_last& ymwdl);

// [time.cal.operators] civil calendar conventional syntax operators    // C++20
constexpr year_month
  operator/(const year& y, const month& m) noexcept;
constexpr year_month
  operator/(const year& y, int m) noexcept;
constexpr month_day
  operator/(const month& m, const day& d) noexcept;
constexpr month_day
  operator/(const month& m, int d) noexcept;
constexpr month_day
  operator/(int m, const day& d) noexcept;
constexpr month_day
  operator/(const day& d, const month& m) noexcept;
constexpr month_day
  operator/(const day& d, int m) noexcept;
constexpr month_day_last
  operator/(const month& m, last_spec) noexcept;
constexpr month_day_last
  operator/(int m, last_spec) noexcept;
constexpr month_day_last
  operator/(last_spec, const month& m) noexcept;
constexpr month_day_last
  operator/(last_spec, int m) noexcept;
constexpr month_weekday
  operator/(const month& m, const weekday_indexed& wdi) noexcept;
constexpr month_weekday
  operator/(int m, const weekday_indexed& wdi) noexcept;
constexpr month_weekday
  operator/(const weekday_indexed& wdi, const month& m) noexcept;
constexpr month_weekday
  operator/(const weekday_indexed& wdi, int m) noexcept;
constexpr month_weekday_last
  operator/(const month& m, const weekday_last& wdl) noexcept;
constexpr month_weekday_last
  operator/(int m, const weekday_last& wdl) noexcept;
constexpr month_weekday_last
  operator/(const weekday_last& wdl, const month& m) noexcept;
constexpr month_weekday_last
  operator/(const weekday_last& wdl, int m) noexcept;
constexpr year_month_day
  operator/(const year_month& ym, const day& d) noexcept;
constexpr year_month_day
  operator/(const year_month& ym, int d) noexcept;
constexpr year_month_day
  operator/(const year& y, const month_day& md) noexcept;
constexpr year_month_day
  operator/(int y, const month_day& md) noexcept;
constexpr year_month_day
  operator/(const month_day& md, const year& y) noexcept;
constexpr year_month_day
  operator/(const month_day& md, int y) noexcept;
constexpr year_month_day_last
  operator/(const year_month& ym, last_spec) noexcept;
constexpr year_month_day_last
  operator/(const year& y, const month_day_last& mdl) noexcept;
constexpr year_month_day_last
  operator/(int y, const month_day_last& mdl) noexcept;
constexpr year_month_day_last
  operator/(const month_day_last& mdl, const year& y) noexcept;
constexpr year_month_day_last
  operator/(const month_day_last& mdl, int y) noexcept;
constexpr year_month_weekday
  operator/(const year_month& ym, const weekday_indexed& wdi) noexcept;
constexpr year_month_weekday
  operator/(const year& y, const month_weekday& mwd) noexcept;
constexpr year_month_weekday
  operator/(int y, const month_weekday& mwd) noexcept;
constexpr year_month_weekday
  operator/(const month_weekday& mwd, const year& y) noexcept;
constexpr year_month_weekday
  operator/(const month_weekday& mwd, int y) noexcept;
constexpr year_month_weekday_last
  operator/(const year_month& ym, const weekday_last& wdl) noexcept;
constexpr year_month_weekday_last
  operator/(const year& y, const month_weekday_last& mwdl) noexcept;
constexpr year_month_weekday_last
  operator/(int y, const month_weekday_last& mwdl) noexcept;
constexpr year_month_weekday_last
  operator/(const month_weekday_last& mwdl, const year& y) noexcept;
constexpr year_month_weekday_last
  operator/(const month_weekday_last& mwdl, int y) noexcept;

// 26.9, class template hh_mm_ss
template <class Duration>
class hh_mm_ss
{
    bool            is_neg; // exposition only
    chrono::hours   h;      // exposition only
    chrono::minutes m;      // exposition only
    chrono::seconds s;      // exposition only
    precision       ss;     // exposition only

public:
    static unsigned constexpr fractional_width = see below;
    using precision                            = see below;

    constexpr hh_mm_ss() noexcept : hh_mm_ss{Duration::zero()} {}
    constexpr explicit hh_mm_ss(Duration d) noexcept;

    constexpr bool is_negative() const noexcept;
    constexpr chrono::hours hours() const noexcept;
    constexpr chrono::minutes minutes() const noexcept;
    constexpr chrono::seconds seconds() const noexcept;
    constexpr precision subseconds() const noexcept;

    constexpr explicit operator  precision()   const noexcept;
    constexpr          precision to_duration() const noexcept;
};

template<class charT, class traits, class Duration>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const hh_mm_ss<Duration>& hms); // C++20

// 26.10, 12/24 hour functions
constexpr bool is_am(hours const& h) noexcept;
constexpr bool is_pm(hours const& h) noexcept;
constexpr hours make12(const hours& h) noexcept;
constexpr hours make24(const hours& h, bool is_pm) noexcept;

// [time.zone.db], time zone database
struct tzdb {                                                                    // C++20
  string                 version;
  vector<time_zone>      zones;
  vector<time_zone_link> links;
  vector<leap_second>    leap_seconds;

  const time_zone* locate_zone(string_view tz_name) const;
  const time_zone* current_zone() const;
};

class tzdb_list {                                                                // C++20
public:
  tzdb_list(const tzdb_list&) = delete;
  tzdb_list& operator=(const tzdb_list&) = delete;

  // unspecified additional constructors

  class const_iterator;

  const tzdb& front() const noexcept;

  const_iterator erase_after(const_iterator p);

  const_iterator begin() const noexcept;
  const_iterator end()   const noexcept;

  const_iterator cbegin() const noexcept;
  const_iterator cend()   const noexcept;
};

// [time.zone.db.access], time zone database access
const tzdb& get_tzdb();                                                          // C++20
tzdb_list& get_tzdb_list();                                                      // C++20
const time_zone* locate_zone(string_view tz_name);                               // C++20
const time_zone* current_zone()                                                  // C++20

// [time.zone.db.remote], remote time zone database support
const tzdb& reload_tzdb();                                                       // C++20
string remote_version();                                                         // C++20

// [time.zone.exception], exception classes
class nonexistent_local_time;                                                    // C++20
class ambiguous_local_time;                                                      // C++20

// [time.zone.info], information classes
struct sys_info {                                                                // C++20
  sys_seconds   begin;
  sys_seconds   end;
  seconds       offset;
  minutes       save;
  string        abbrev;
};

template<class charT, class traits>                                              // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const sys_info& si);

struct local_info {                                                             // C++20
  static constexpr int unique      = 0;
  static constexpr int nonexistent = 1;
  static constexpr int ambiguous   = 2;

  int result;
  sys_info first;
  sys_info second;
};

template<class charT, class traits>                                              // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const local_info& li);

// [time.zone.timezone] class time_zone                                                      // C++20
enum class choose {earliest, latest};
class time_zone {
  time_zone(time_zone&&) = default;
  time_zone& operator=(time_zone&&) = default;

  // unspecified additional constructors

  string_view name() const noexcept;

  template<class Duration>
  sys_info get_info(const sys_time<Duration>& st) const;

  template<class Duration>
  local_info get_info(const local_time<Duration>& tp) const;

  template<class Duration>
  sys_time<common_type_t<Duration, seconds>>
    to_sys(const local_time<Duration>& tp) const;

  template<class Duration>
  sys_time<common_type_t<Duration, seconds>>
    to_sys(const local_time<Duration>& tp, choose z) const;

  template<class Duration>
  local_time<common_type_t<Duration, seconds>>
    to_local(const sys_time<Duration>& tp) const;
};
bool operator==(const time_zone& x, const time_zone& y) noexcept;                // C++20
strong_ordering operator<=>(const time_zone& x, const time_zone& y) noexcept;    // C++20

// [time.zone.zonedtraits], class template zoned_traits
template<class T> struct zoned_traits;                                           // C++20

// [time.zone.zonedtime], class template zoned_time
template<class Duration, class TimeZonePtr = const time_zone*>                   // C++20
class zoned_time;

using zoned_seconds = zoned_time<seconds>;                                       // C++20

template<class Duration1, class Duration2, class TimeZonePtr>                    // C++20
  bool operator==(const zoned_time<Duration1, TimeZonePtr>& x,
                  const zoned_time<Duration2, TimeZonePtr>& y);

template<class charT, class traits, class Duration, class TimeZonePtr>           // C++20
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os,
               const zoned_time<Duration, TimeZonePtr>& t);

// [time.zone.leap], leap second support
class leap_second {                                                              // C++20
public:
  leap_second(const leap_second&)            = default;
  leap_second& operator=(const leap_second&) = default;

  // unspecified additional constructors

  constexpr sys_seconds date() const noexcept;
  constexpr seconds value() const noexcept;
};

constexpr bool operator==(const leap_second& x, const leap_second& y);           // C++20
constexpr strong_ordering operator<=>(const leap_second& x, const leap_second& y);

template<class Duration>                                                         // C++20
  constexpr bool operator==(const leap_second& x, const sys_time<Duration>& y);
template<class Duration>                                                         // C++20
  constexpr bool operator< (const leap_second& x, const sys_time<Duration>& y);
template<class Duration>                                                         // C++20
  constexpr bool operator< (const sys_time<Duration>& x, const leap_second& y);
template<class Duration>                                                         // C++20
  constexpr bool operator> (const leap_second& x, const sys_time<Duration>& y);
template<class Duration>                                                         // C++20
  constexpr bool operator> (const sys_time<Duration>& x, const leap_second& y);
template<class Duration>                                                         // C++20
  constexpr bool operator<=(const leap_second& x, const sys_time<Duration>& y);
template<class Duration>                                                         // C++20
  constexpr bool operator<=(const sys_time<Duration>& x, const leap_second& y);
template<class Duration>                                                         // C++20
  constexpr bool operator>=(const leap_second& x, const sys_time<Duration>& y);
template<class Duration>                                                         // C++20
  constexpr bool operator>=(const sys_time<Duration>& x, const leap_second& y);
template<class Duration>                                                         // C++20
  requires three_way_comparable_with<sys_seconds, sys_time<Duration>>
  constexpr auto operator<=>(const leap_second& x, const sys_time<Duration>& y);

// [time.zone.link], class time_zone_link
class time_zone_link {                                                           // C++20
public:
  time_zone_link(time_zone_link&&)            = default;
  time_zone_link& operator=(time_zone_link&&) = default;

  // unspecified additional constructors

  string_view name()   const noexcept;
  string_view target() const noexcept;
};

bool operator==(const time_zone_link& x, const time_zone_link& y);               // C++20
strong_ordering operator<=>(const time_zone_link& x, const time_zone_link& y);   // C++20

}  // chrono

namespace std {
  template<class Rep, class Period, class charT>
    struct formatter<chrono::duration<Rep, Period>, charT>;                       // C++20
  template<class Duration, class charT>
    struct formatter<chrono::sys_time<Duration>, charT>;                          // C++20
  template<class Duration, class charT>
    struct formatter<chrono::utc_time<Duration>, charT>;                          // C++20
  template<class Duration, class charT>
    struct formatter<chrono::tai_time<Duration>, charT>;                          // C++20
  template<class Duration, class charT>
    struct formatter<chrono::gps_time<Duration>, charT>;                          // C++20
  template<class Duration, class charT>
    struct formatter<chrono::file_time<Duration>, charT>;                         // C++20
  template<class Duration, class charT>
    struct formatter<chrono::local_time<Duration>, charT>;                        // C++20
  template<class charT> struct formatter<chrono::day, charT>;                     // C++20
  template<class charT> struct formatter<chrono::month, charT>;                   // C++20
  template<class charT> struct formatter<chrono::year, charT>;                    // C++20
  template<class charT> struct formatter<chrono::weekday, charT>;                 // C++20
  template<class charT> struct formatter<chrono::weekday_indexed, charT>;         // C++20
  template<class charT> struct formatter<chrono::weekday_last, charT>;            // C++20
  template<class charT> struct formatter<chrono::month_day, charT>;               // C++20
  template<class charT> struct formatter<chrono::month_day_last, charT>;          // C++20
  template<class charT> struct formatter<chrono::month_weekday, charT>;           // C++20
  template<class charT> struct formatter<chrono::month_weekday_last, charT>;      // C++20
  template<class charT> struct formatter<chrono::year_month, charT>;              // C++20
  template<class charT> struct formatter<chrono::year_month_day, charT>;          // C++20
  template<class charT> struct formatter<chrono::year_month_day_last, charT>;     // C++20
  template<class charT> struct formatter<chrono::year_month_weekday, charT>;      // C++20
  template<class charT> struct formatter<chrono::year_month_weekday_last, charT>; // C++20
  template<class Rep, class Period, class charT>
    struct formatter<chrono::hh_mm_ss<duration<Rep, Period>>, charT>;             // C++20
  template<class charT> struct formatter<chrono::sys_info, charT>;                // C++20
  template<class charT> struct formatter<chrono::local_info, charT>;              // C++20
  template<class Duration, class TimeZonePtr, class charT>                        // C++20
    struct formatter<chrono::zoned_time<Duration, TimeZonePtr>, charT>;
} // namespace std

namespace chrono {
// calendrical constants
inline constexpr last_spec                              last{};       // C++20
inline constexpr chrono::weekday                        Sunday{0};    // C++20
inline constexpr chrono::weekday                        Monday{1};    // C++20
inline constexpr chrono::weekday                        Tuesday{2};   // C++20
inline constexpr chrono::weekday                        Wednesday{3}; // C++20
inline constexpr chrono::weekday                        Thursday{4};  // C++20
inline constexpr chrono::weekday                        Friday{5};    // C++20
inline constexpr chrono::weekday                        Saturday{6};  // C++20

inline constexpr chrono::month                          January{1};   // C++20
inline constexpr chrono::month                          February{2};  // C++20
inline constexpr chrono::month                          March{3};     // C++20
inline constexpr chrono::month                          April{4};     // C++20
inline constexpr chrono::month                          May{5};       // C++20
inline constexpr chrono::month                          June{6};      // C++20
inline constexpr chrono::month                          July{7};      // C++20
inline constexpr chrono::month                          August{8};    // C++20
inline constexpr chrono::month                          September{9}; // C++20
inline constexpr chrono::month                          October{10};  // C++20
inline constexpr chrono::month                          November{11}; // C++20
inline constexpr chrono::month                          December{12}; // C++20
}  // chrono

inline namespace literals {
  inline namespace chrono_literals {
constexpr chrono::hours                                 operator ""h(unsigned long long); // C++14
constexpr chrono::duration<unspecified , ratio<3600,1>> operator ""h(long double); // C++14
constexpr chrono::minutes                               operator ""min(unsigned long long); // C++14
constexpr chrono::duration<unspecified , ratio<60,1>>   operator ""min(long double); // C++14
constexpr chrono::seconds                               operator ""s(unsigned long long); // C++14
constexpr chrono::duration<unspecified >                operator ""s(long double); // C++14
constexpr chrono::milliseconds                          operator ""ms(unsigned long long); // C++14
constexpr chrono::duration<unspecified , milli>         operator ""ms(long double); // C++14
constexpr chrono::microseconds                          operator ""us(unsigned long long); // C++14
constexpr chrono::duration<unspecified , micro>         operator ""us(long double); // C++14
constexpr chrono::nanoseconds                           operator ""ns(unsigned long long); // C++14
constexpr chrono::duration<unspecified , nano>          operator ""ns(long double); // C++14
constexpr chrono::day                                   operator ""d(unsigned long long d) noexcept; // C++20
constexpr chrono::year                                  operator ""y(unsigned long long y) noexcept; // C++20
}  // chrono_literals
}  // literals

}  // std
*/

// clang-format on

#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
#  include <__cxx03/chrono>
#else
#  include <__config>

#  include <__chrono/duration.h>
#  include <__chrono/file_clock.h>
#  include <__chrono/high_resolution_clock.h>
#  include <__chrono/steady_clock.h>
#  include <__chrono/system_clock.h>
#  include <__chrono/time_point.h>

#  if _LIBCPP_STD_VER >= 20
#    include <__chrono/calendar.h>
#    include <__chrono/day.h>
#    include <__chrono/exception.h>
#    include <__chrono/hh_mm_ss.h>
#    include <__chrono/literals.h>
#    include <__chrono/local_info.h>
#    include <__chrono/month.h>
#    include <__chrono/month_weekday.h>
#    include <__chrono/monthday.h>
#    include <__chrono/sys_info.h>
#    include <__chrono/weekday.h>
#    include <__chrono/year.h>
#    include <__chrono/year_month.h>
#    include <__chrono/year_month_day.h>
#    include <__chrono/year_month_weekday.h>

#    if _LIBCPP_HAS_LOCALIZATION
#      include <__chrono/formatter.h>
#      include <__chrono/ostream.h>
#      include <__chrono/parser_std_format_spec.h>
#      include <__chrono/statically_widen.h>
#    endif

#    if _LIBCPP_HAS_TIME_ZONE_DATABASE && _LIBCPP_HAS_FILESYSTEM && _LIBCPP_HAS_LOCALIZATION
#      include <__chrono/gps_clock.h>
#      include <__chrono/leap_second.h>
#      include <__chrono/tai_clock.h>
#      include <__chrono/time_zone.h>
#      include <__chrono/time_zone_link.h>
#      include <__chrono/tzdb.h>
#      include <__chrono/tzdb_list.h>
#      include <__chrono/utc_clock.h>
#      include <__chrono/zoned_time.h>
#    endif

#  endif

#  include <version>

// standard-mandated includes

// [time.syn]
#  include <compare>

#  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#    pragma GCC system_header
#  endif

#  if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 17
#    include <cstdint>
#    include <stdexcept>
#    include <string_view>
#  endif

#  if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
#    include <bit>
#    include <concepts>
#    include <cstring>
#    include <forward_list>
#    include <string>
#    include <tuple>
#    include <vector>
#  endif

#  if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER == 20
#    include <charconv>
#    if _LIBCPP_HAS_LOCALIZATION
#      include <locale>
#      include <ostream>
#    endif
#  endif
#endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)

#endif // _LIBCPP_CHRONO