// -*- C++ -*-
//===---------------------------- chrono ----------------------------------===//
//
// 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

/*
    chrono synopsis

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<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

    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 {


template<class T> struct is_clock;  // C++20
template<class T> inline constexpr bool is_clock_v = is_clock<T>::value;   // C++20


// 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);
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);

// 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 is elsewhere

// 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);
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);

// 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

class utc_clock;                                        // C++20

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

class tai_clock;                                        // C++20

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

class file_clock;                                       // C++20

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

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;

// 25.7.8, 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>;

// 25.7.9, time_point conversions template<class DestClock, class SourceClock>    // C++20
struct clock_time_conversion;

template<class DestClock, class SourceClock, class Duration>
  auto clock_cast(const time_point<SourceClock, Duration>& t);

// 25.8.2, class last_spec    // C++20
struct last_spec;

// 25.8.3, class day          // C++20

class day;
constexpr bool operator==(const day& x, const day& y) noexcept;
constexpr bool operator!=(const day& x, const day& y) noexcept;
constexpr bool operator< (const day& x, const day& y) noexcept;
constexpr bool operator> (const day& x, const day& y) noexcept;
constexpr bool operator<=(const day& x, const day& y) noexcept;
constexpr bool 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;

// 25.8.4, class month    // C++20
class month;
constexpr bool operator==(const month& x, const month& y) noexcept;
constexpr bool operator!=(const month& x, const month& y) noexcept;
constexpr bool operator< (const month& x, const month& y) noexcept;
constexpr bool operator> (const month& x, const month& y) noexcept;
constexpr bool operator<=(const month& x, const month& y) noexcept;
constexpr bool 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;

// 25.8.5, class year    // C++20
class year;
constexpr bool operator==(const year& x, const year& y) noexcept;
constexpr bool operator!=(const year& x, const year& y) noexcept;
constexpr bool operator< (const year& x, const year& y) noexcept;
constexpr bool operator> (const year& x, const year& y) noexcept;
constexpr bool operator<=(const year& x, const year& y) noexcept;
constexpr bool 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;

// 25.8.6, class weekday    // C++20
class weekday;

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

// 25.8.7, class weekday_indexed    // C++20

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

// 25.8.8, class weekday_last    // C++20
class weekday_last;

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

// 25.8.9, class month_day    // C++20
class month_day;

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


// 25.8.10, 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 bool operator!=(const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator< (const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator> (const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator<=(const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator>=(const month_day_last& x, const month_day_last& y) noexcept;

// 25.8.11, class month_weekday    // C++20
class month_weekday;

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

// 25.8.12, class month_weekday_last    // C++20
class month_weekday_last;

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


// 25.8.13, class year_month    // C++20
class year_month;

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

// 25.8.14, 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 bool operator!=(const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool operator< (const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool operator> (const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool operator<=(const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool 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;


// 25.8.15, 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 bool operator!=(const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator< (const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator> (const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator<=(const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator>=(const year_month_day_last& x,
                          const year_month_day_last& 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;

// 25.8.16, 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 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;

// 25.8.17, 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 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;

// 25.8.18, 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;

// 25.9, class template time_of_day    // C++20
template<class Duration> class time_of_day;

template<> class time_of_day<hours>;
template<> class time_of_day<minutes>;
template<> class time_of_day<seconds>;
template<class Rep, class Period> class time_of_day<duration<Rep, Period>>;

// 25.10.2, time zone database     // C++20
struct tzdb;
class tzdb_list;

// 25.10.2.3, time zone database access    // C++20
const tzdb& get_tzdb();
tzdb_list& get_tzdb_list();
const time_zone* locate_zone(string_view tz_name);
const time_zone* current_zone();

// 25.10.2.4, remote time zone database support    // C++20
const tzdb& reload_tzdb();
string remote_version();

// 25.10.3, exception classes    // C++20
class nonexistent_local_time;
class ambiguous_local_time;

// 25.10.4, information classes    // C++20
struct sys_info;
struct local_info;

// 25.10.5, class time_zone    // C++20
enum class choose {earliest, latest};
class time_zone;
bool operator==(const time_zone& x, const time_zone& y) noexcept;
bool operator!=(const time_zone& x, const time_zone& y) noexcept;
bool operator<(const time_zone& x, const time_zone& y) noexcept;
bool operator>(const time_zone& x, const time_zone& y) noexcept;
bool operator<=(const time_zone& x, const time_zone& y) noexcept;
bool operator>=(const time_zone& x, const time_zone& y) noexcept;

// 25.10.6, class template zoned_traits    // C++20
template<class T> struct zoned_traits;

// 25.10.7, class template zoned_time    // C++20
template<class Duration, class TimeZonePtr = const time_zone*> class zoned_time;
using zoned_seconds = zoned_time<seconds>;

template<class Duration1, class Duration2, class TimeZonePtr>
  bool operator==(const zoned_time<Duration1, TimeZonePtr>& x,
                  const zoned_time<Duration2, TimeZonePtr>& y);
template<class Duration1, class Duration2, class TimeZonePtr>
  bool operator!=(const zoned_time<Duration1, TimeZonePtr>& x,
                  const zoned_time<Duration2, TimeZonePtr>& y);

// 25.10.8, leap second support    // C++20
class leap;

bool operator==(const leap& x, const leap& y);
bool operator!=(const leap& x, const leap& y);
bool operator< (const leap& x, const leap& y);
bool operator> (const leap& x, const leap& y);
bool operator<=(const leap& x, const leap& y);
bool operator>=(const leap& x, const leap& y);
template<class Duration>
  bool operator==(const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator==(const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator!=(const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator!=(const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator< (const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator< (const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator> (const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator> (const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator<=(const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator<=(const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator>=(const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator>=(const sys_time<Duration>& x, const leap& y);

// 25.10.9, class link    // C++20
class link;
bool operator==(const link& x, const link& y);
bool operator!=(const link& x, const link& y);
bool operator< (const link& x, const link& y);
bool operator> (const link& x, const link& y);
bool operator<=(const link& x, const link& y);
bool operator>=(const link& x, const link& y);

// 25.11, formatting    // C++20
template<class charT, class Streamable>
  basic_string<charT>
    format(const charT* fmt, const Streamable& s);

template<class charT, class Streamable>
  basic_string<charT>
    format(const locale& loc, const charT* fmt, const Streamable& s);

template<class charT, class traits, class Alloc, class Streamable>
  basic_string<charT, traits, Alloc>
    format(const basic_string<charT, traits, Alloc>& fmt, const Streamable& s);

template<class charT, class traits, class Alloc, class Streamable>
  basic_string<charT, traits, Alloc>
    format(const locale& loc, const basic_string<charT, traits, Alloc>& fmt,
           const Streamable& s);

// 25.12, parsing    // C++20
template<class charT, class traits, class Alloc, class Parsable>
unspecified
    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp);

template<class charT, class traits, class Alloc, class Parsable>
unspecified
    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
          basic_string<charT, traits, Alloc>& abbrev);

template<class charT, class traits, class Alloc, class Parsable>
unspecified
    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
          minutes& offset);

template<class charT, class traits, class Alloc, class Parsable>
unspecified
    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
          basic_string<charT, traits, Alloc>& abbrev, minutes& offset);

// 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
*/

#include <__config>
#include <ctime>
#include <type_traits>
#include <ratio>
#include <limits>
#include <version>

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

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

#ifndef _LIBCPP_CXX03_LANG
_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
struct _FilesystemClock;
_LIBCPP_END_NAMESPACE_FILESYSTEM
#endif // !_LIBCPP_CXX03_LANG

_LIBCPP_BEGIN_NAMESPACE_STD

namespace chrono
{

template <class _Rep, class _Period = ratio<1> > class _LIBCPP_TEMPLATE_VIS duration;

template <class _Tp>
struct __is_duration : false_type {};

template <class _Rep, class _Period>
struct __is_duration<duration<_Rep, _Period> > : true_type  {};

template <class _Rep, class _Period>
struct __is_duration<const duration<_Rep, _Period> > : true_type  {};

template <class _Rep, class _Period>
struct __is_duration<volatile duration<_Rep, _Period> > : true_type  {};

template <class _Rep, class _Period>
struct __is_duration<const volatile duration<_Rep, _Period> > : true_type  {};

} // chrono

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
struct _LIBCPP_TEMPLATE_VIS common_type<chrono::duration<_Rep1, _Period1>,
                                         chrono::duration<_Rep2, _Period2> >
{
    typedef chrono::duration<typename common_type<_Rep1, _Rep2>::type,
                             typename __ratio_gcd<_Period1, _Period2>::type> type;
};

namespace chrono {

// duration_cast

template <class _FromDuration, class _ToDuration,
          class _Period = typename ratio_divide<typename _FromDuration::period, typename _ToDuration::period>::type,
          bool = _Period::num == 1,
          bool = _Period::den == 1>
struct __duration_cast;

template <class _FromDuration, class _ToDuration, class _Period>
struct __duration_cast<_FromDuration, _ToDuration, _Period, true, true>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    _ToDuration operator()(const _FromDuration& __fd) const
    {
        return _ToDuration(static_cast<typename _ToDuration::rep>(__fd.count()));
    }
};

template <class _FromDuration, class _ToDuration, class _Period>
struct __duration_cast<_FromDuration, _ToDuration, _Period, true, false>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    _ToDuration operator()(const _FromDuration& __fd) const
    {
        typedef typename common_type<typename _ToDuration::rep, typename _FromDuration::rep, intmax_t>::type _Ct;
        return _ToDuration(static_cast<typename _ToDuration::rep>(
                           static_cast<_Ct>(__fd.count()) / static_cast<_Ct>(_Period::den)));
    }
};

template <class _FromDuration, class _ToDuration, class _Period>
struct __duration_cast<_FromDuration, _ToDuration, _Period, false, true>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    _ToDuration operator()(const _FromDuration& __fd) const
    {
        typedef typename common_type<typename _ToDuration::rep, typename _FromDuration::rep, intmax_t>::type _Ct;
        return _ToDuration(static_cast<typename _ToDuration::rep>(
                           static_cast<_Ct>(__fd.count()) * static_cast<_Ct>(_Period::num)));
    }
};

template <class _FromDuration, class _ToDuration, class _Period>
struct __duration_cast<_FromDuration, _ToDuration, _Period, false, false>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    _ToDuration operator()(const _FromDuration& __fd) const
    {
        typedef typename common_type<typename _ToDuration::rep, typename _FromDuration::rep, intmax_t>::type _Ct;
        return _ToDuration(static_cast<typename _ToDuration::rep>(
                           static_cast<_Ct>(__fd.count()) * static_cast<_Ct>(_Period::num)
                                                          / static_cast<_Ct>(_Period::den)));
    }
};

template <class _ToDuration, class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    _ToDuration
>::type
duration_cast(const duration<_Rep, _Period>& __fd)
{
    return __duration_cast<duration<_Rep, _Period>, _ToDuration>()(__fd);
}

template <class _Rep>
struct _LIBCPP_TEMPLATE_VIS treat_as_floating_point : is_floating_point<_Rep> {};

#if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
template <class _Rep>
_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool treat_as_floating_point_v
    = treat_as_floating_point<_Rep>::value;
#endif

template <class _Rep>
struct _LIBCPP_TEMPLATE_VIS duration_values
{
public:
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR _Rep zero() _NOEXCEPT {return _Rep(0);}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR _Rep max()  _NOEXCEPT {return numeric_limits<_Rep>::max();}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR _Rep min()  _NOEXCEPT {return numeric_limits<_Rep>::lowest();}
};

#if _LIBCPP_STD_VER > 14
template <class _ToDuration, class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    _ToDuration
>::type
floor(const duration<_Rep, _Period>& __d)
{
    _ToDuration __t = duration_cast<_ToDuration>(__d);
    if (__t > __d)
        __t = __t - _ToDuration{1};
    return __t;
}

template <class _ToDuration, class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    _ToDuration
>::type
ceil(const duration<_Rep, _Period>& __d)
{
    _ToDuration __t = duration_cast<_ToDuration>(__d);
    if (__t < __d)
        __t = __t + _ToDuration{1};
    return __t;
}

template <class _ToDuration, class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    _ToDuration
>::type
round(const duration<_Rep, _Period>& __d)
{
    _ToDuration __lower = floor<_ToDuration>(__d);
    _ToDuration __upper = __lower + _ToDuration{1};
    auto __lowerDiff = __d - __lower;
    auto __upperDiff = __upper - __d;
    if (__lowerDiff < __upperDiff)
        return __lower;
    if (__lowerDiff > __upperDiff)
        return __upper;
    return __lower.count() & 1 ? __upper : __lower;
}
#endif

// duration

template <class _Rep, class _Period>
class _LIBCPP_TEMPLATE_VIS 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");

    template <class _R1, class _R2>
    struct __no_overflow
    {
    private:
        static const intmax_t __gcd_n1_n2 = __static_gcd<_R1::num, _R2::num>::value;
        static const intmax_t __gcd_d1_d2 = __static_gcd<_R1::den, _R2::den>::value;
        static const intmax_t __n1 = _R1::num / __gcd_n1_n2;
        static const intmax_t __d1 = _R1::den / __gcd_d1_d2;
        static const intmax_t __n2 = _R2::num / __gcd_n1_n2;
        static const intmax_t __d2 = _R2::den / __gcd_d1_d2;
        static const intmax_t max = -((intmax_t(1) << (sizeof(intmax_t) * CHAR_BIT - 1)) + 1);

        template <intmax_t _Xp, intmax_t _Yp, bool __overflow>
        struct __mul    // __overflow == false
        {
            static const intmax_t value = _Xp * _Yp;
        };

        template <intmax_t _Xp, intmax_t _Yp>
        struct __mul<_Xp, _Yp, true>
        {
            static const intmax_t value = 1;
        };

    public:
        static const bool value = (__n1 <= max / __d2) && (__n2 <= max / __d1);
        typedef ratio<__mul<__n1, __d2, !value>::value,
                      __mul<__n2, __d1, !value>::value> type;
    };

public:
    typedef _Rep rep;
    typedef typename _Period::type period;
private:
    rep __rep_;
public:

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
#ifndef _LIBCPP_CXX03_LANG
        duration() = default;
#else
        duration() {}
#endif

    template <class _Rep2>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
        explicit duration(const _Rep2& __r,
            typename enable_if
            <
               is_convertible<_Rep2, rep>::value &&
               (treat_as_floating_point<rep>::value ||
               !treat_as_floating_point<_Rep2>::value)
            >::type* = 0)
                : __rep_(__r) {}

    // conversions
    template <class _Rep2, class _Period2>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
        duration(const duration<_Rep2, _Period2>& __d,
            typename enable_if
            <
                __no_overflow<_Period2, period>::value && (
                treat_as_floating_point<rep>::value ||
                (__no_overflow<_Period2, period>::type::den == 1 &&
                 !treat_as_floating_point<_Rep2>::value))
            >::type* = 0)
                : __rep_(_VSTD::chrono::duration_cast<duration>(__d).count()) {}

    // observer

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR rep count() const {return __rep_;}

    // arithmetic

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator+() const {return typename common_type<duration>::type(*this);}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator-() const {return typename common_type<duration>::type(-__rep_);}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator++()      {++__rep_; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration  operator++(int)   {return duration(__rep_++);}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator--()      {--__rep_; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration  operator--(int)   {return duration(__rep_--);}

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator+=(const duration& __d) {__rep_ += __d.count(); return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator-=(const duration& __d) {__rep_ -= __d.count(); return *this;}

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator*=(const rep& rhs) {__rep_ *= rhs; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator/=(const rep& rhs) {__rep_ /= rhs; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator%=(const rep& rhs) {__rep_ %= rhs; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator%=(const duration& rhs) {__rep_ %= rhs.count(); return *this;}

    // special values

    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR duration zero() _NOEXCEPT {return duration(duration_values<rep>::zero());}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR duration min()  _NOEXCEPT {return duration(duration_values<rep>::min());}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR duration max()  _NOEXCEPT {return duration(duration_values<rep>::max());}
};

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;
#if _LIBCPP_STD_VER > 17
typedef duration<     int, ratio_multiply<ratio<24>, hours::period>>         days;
typedef duration<     int, ratio_multiply<ratio<7>,   days::period>>         weeks;
typedef duration<     int, ratio_multiply<ratio<146097, 400>, days::period>> years;
typedef duration<     int, ratio_divide<years::period, ratio<12>>>           months;
#endif
// Duration ==

template <class _LhsDuration, class _RhsDuration>
struct __duration_eq
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    bool operator()(const _LhsDuration& __lhs, const _RhsDuration& __rhs) const
        {
            typedef typename common_type<_LhsDuration, _RhsDuration>::type _Ct;
            return _Ct(__lhs).count() == _Ct(__rhs).count();
        }
};

template <class _LhsDuration>
struct __duration_eq<_LhsDuration, _LhsDuration>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    bool operator()(const _LhsDuration& __lhs, const _LhsDuration& __rhs) const
        {return __lhs.count() == __rhs.count();}
};

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator==(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return __duration_eq<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >()(__lhs, __rhs);
}

// Duration !=

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator!=(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return !(__lhs == __rhs);
}

// Duration <

template <class _LhsDuration, class _RhsDuration>
struct __duration_lt
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    bool operator()(const _LhsDuration& __lhs, const _RhsDuration& __rhs) const
        {
            typedef typename common_type<_LhsDuration, _RhsDuration>::type _Ct;
            return _Ct(__lhs).count() < _Ct(__rhs).count();
        }
};

template <class _LhsDuration>
struct __duration_lt<_LhsDuration, _LhsDuration>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    bool operator()(const _LhsDuration& __lhs, const _LhsDuration& __rhs) const
        {return __lhs.count() < __rhs.count();}
};

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator< (const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return __duration_lt<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >()(__lhs, __rhs);
}

// Duration >

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator> (const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return __rhs < __lhs;
}

// Duration <=

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator<=(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return !(__rhs < __lhs);
}

// Duration >=

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator>=(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return !(__lhs < __rhs);
}

// Duration +

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type
operator+(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Cd;
    return _Cd(_Cd(__lhs).count() + _Cd(__rhs).count());
}

// Duration -

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type
operator-(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Cd;
    return _Cd(_Cd(__lhs).count() - _Cd(__rhs).count());
}

// Duration *

template <class _Rep1, class _Period, class _Rep2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename enable_if
<
    is_convertible<_Rep2, typename common_type<_Rep1, _Rep2>::type>::value,
    duration<typename common_type<_Rep1, _Rep2>::type, _Period>
>::type
operator*(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
{
    typedef typename common_type<_Rep1, _Rep2>::type _Cr;
    typedef duration<_Cr, _Period> _Cd;
    return _Cd(_Cd(__d).count() * static_cast<_Cr>(__s));
}

template <class _Rep1, class _Period, class _Rep2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename enable_if
<
    is_convertible<_Rep1, typename common_type<_Rep1, _Rep2>::type>::value,
    duration<typename common_type<_Rep1, _Rep2>::type, _Period>
>::type
operator*(const _Rep1& __s, const duration<_Rep2, _Period>& __d)
{
    return __d * __s;
}

// Duration /

template <class _Rep1, class _Period, class _Rep2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename enable_if
<
    !__is_duration<_Rep2>::value &&
      is_convertible<_Rep2, typename common_type<_Rep1, _Rep2>::type>::value,
    duration<typename common_type<_Rep1, _Rep2>::type, _Period>
>::type
operator/(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
{
    typedef typename common_type<_Rep1, _Rep2>::type _Cr;
    typedef duration<_Cr, _Period> _Cd;
    return _Cd(_Cd(__d).count() / static_cast<_Cr>(__s));
}

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename common_type<_Rep1, _Rep2>::type
operator/(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Ct;
    return _Ct(__lhs).count() / _Ct(__rhs).count();
}

// Duration %

template <class _Rep1, class _Period, class _Rep2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename enable_if
<
    !__is_duration<_Rep2>::value &&
      is_convertible<_Rep2, typename common_type<_Rep1, _Rep2>::type>::value,
    duration<typename common_type<_Rep1, _Rep2>::type, _Period>
>::type
operator%(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
{
    typedef typename common_type<_Rep1, _Rep2>::type _Cr;
    typedef duration<_Cr, _Period> _Cd;
    return _Cd(_Cd(__d).count() % static_cast<_Cr>(__s));
}

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type
operator%(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef typename common_type<_Rep1, _Rep2>::type _Cr;
    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Cd;
    return _Cd(static_cast<_Cr>(_Cd(__lhs).count()) % static_cast<_Cr>(_Cd(__rhs).count()));
}

//////////////////////////////////////////////////////////
///////////////////// time_point /////////////////////////
//////////////////////////////////////////////////////////

template <class _Clock, class _Duration = typename _Clock::duration>
class _LIBCPP_TEMPLATE_VIS time_point
{
    static_assert(__is_duration<_Duration>::value,
                  "Second template parameter of time_point must be a std::chrono::duration");
public:
    typedef _Clock                    clock;
    typedef _Duration                 duration;
    typedef typename duration::rep    rep;
    typedef typename duration::period period;
private:
    duration __d_;

public:
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 time_point() : __d_(duration::zero()) {}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 explicit time_point(const duration& __d) : __d_(__d) {}

    // conversions
    template <class _Duration2>
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    time_point(const time_point<clock, _Duration2>& t,
        typename enable_if
        <
            is_convertible<_Duration2, duration>::value
        >::type* = 0)
            : __d_(t.time_since_epoch()) {}

    // observer

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 duration time_since_epoch() const {return __d_;}

    // arithmetic

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 time_point& operator+=(const duration& __d) {__d_ += __d; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 time_point& operator-=(const duration& __d) {__d_ -= __d; return *this;}

    // special values

    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR time_point min() _NOEXCEPT {return time_point(duration::min());}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR time_point max() _NOEXCEPT {return time_point(duration::max());}
};

} // chrono

template <class _Clock, class _Duration1, class _Duration2>
struct _LIBCPP_TEMPLATE_VIS common_type<chrono::time_point<_Clock, _Duration1>,
                                         chrono::time_point<_Clock, _Duration2> >
{
    typedef chrono::time_point<_Clock, typename common_type<_Duration1, _Duration2>::type> type;
};

namespace chrono {

template <class _ToDuration, class _Clock, class _Duration>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
time_point<_Clock, _ToDuration>
time_point_cast(const time_point<_Clock, _Duration>& __t)
{
    return time_point<_Clock, _ToDuration>(_VSTD::chrono::duration_cast<_ToDuration>(__t.time_since_epoch()));
}

#if _LIBCPP_STD_VER > 14
template <class _ToDuration, class _Clock, class _Duration>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    time_point<_Clock, _ToDuration>
>::type
floor(const time_point<_Clock, _Duration>& __t)
{
    return time_point<_Clock, _ToDuration>{floor<_ToDuration>(__t.time_since_epoch())};
}

template <class _ToDuration, class _Clock, class _Duration>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    time_point<_Clock, _ToDuration>
>::type
ceil(const time_point<_Clock, _Duration>& __t)
{
    return time_point<_Clock, _ToDuration>{ceil<_ToDuration>(__t.time_since_epoch())};
}

template <class _ToDuration, class _Clock, class _Duration>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    time_point<_Clock, _ToDuration>
>::type
round(const time_point<_Clock, _Duration>& __t)
{
    return time_point<_Clock, _ToDuration>{round<_ToDuration>(__t.time_since_epoch())};
}

template <class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    numeric_limits<_Rep>::is_signed,
    duration<_Rep, _Period>
>::type
abs(duration<_Rep, _Period> __d)
{
    return __d >= __d.zero() ? __d : -__d;
}
#endif

// time_point ==

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator==(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __lhs.time_since_epoch() == __rhs.time_since_epoch();
}

// time_point !=

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator!=(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return !(__lhs == __rhs);
}

// time_point <

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator<(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __lhs.time_since_epoch() < __rhs.time_since_epoch();
}

// time_point >

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator>(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __rhs < __lhs;
}

// time_point <=

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator<=(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return !(__rhs < __lhs);
}

// time_point >=

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator>=(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return !(__lhs < __rhs);
}

// time_point operator+(time_point x, duration y);

template <class _Clock, class _Duration1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type>
operator+(const time_point<_Clock, _Duration1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type> _Tr;
    return _Tr (__lhs.time_since_epoch() + __rhs);
}

// time_point operator+(duration x, time_point y);

template <class _Rep1, class _Period1, class _Clock, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
time_point<_Clock, typename common_type<duration<_Rep1, _Period1>, _Duration2>::type>
operator+(const duration<_Rep1, _Period1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __rhs + __lhs;
}

// time_point operator-(time_point x, duration y);

template <class _Clock, class _Duration1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type>
operator-(const time_point<_Clock, _Duration1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type> _Ret;
    return _Ret(__lhs.time_since_epoch() -__rhs);
}

// duration operator-(time_point x, time_point y);

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
typename common_type<_Duration1, _Duration2>::type
operator-(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __lhs.time_since_epoch() - __rhs.time_since_epoch();
}

//////////////////////////////////////////////////////////
/////////////////////// clocks ///////////////////////////
//////////////////////////////////////////////////////////

class _LIBCPP_TYPE_VIS system_clock
{
public:
    typedef microseconds                     duration;
    typedef duration::rep                    rep;
    typedef duration::period                 period;
    typedef chrono::time_point<system_clock> time_point;
    static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;

    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;
};

#ifndef _LIBCPP_HAS_NO_MONOTONIC_CLOCK
class _LIBCPP_TYPE_VIS steady_clock
{
public:
    typedef nanoseconds                                   duration;
    typedef duration::rep                                 rep;
    typedef duration::period                              period;
    typedef chrono::time_point<steady_clock, duration>    time_point;
    static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = true;

    static time_point now() _NOEXCEPT;
};

typedef steady_clock high_resolution_clock;
#else
typedef system_clock high_resolution_clock;
#endif

#if _LIBCPP_STD_VER > 17
// [time.clock.file], type file_clock
using file_clock = _VSTD_FS::_FilesystemClock;

template<class _Duration>
using file_time = time_point<file_clock, _Duration>;


template <class _Duration>
using sys_time    = time_point<system_clock, _Duration>;
using sys_seconds = sys_time<seconds>;
using sys_days    = sys_time<days>;

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>;


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

class day {
private:
    unsigned char __d;
public:
    day() = default;
    explicit inline constexpr day(unsigned __val) noexcept : __d(static_cast<unsigned char>(__val)) {}
    inline constexpr day& operator++()    noexcept { ++__d; return *this; }
    inline constexpr day  operator++(int) noexcept { day __tmp = *this; ++(*this); return __tmp; }
    inline constexpr day& operator--()    noexcept { --__d; return *this; }
    inline constexpr day  operator--(int) noexcept { day __tmp = *this; --(*this); return __tmp; }
           constexpr day& operator+=(const days& __dd) noexcept;
           constexpr day& operator-=(const days& __dd) noexcept;
    explicit inline constexpr operator unsigned() const noexcept { return __d; }
    inline constexpr bool ok() const noexcept { return __d >= 1 && __d <= 31; }
  };


inline constexpr
bool operator==(const day& __lhs, const day& __rhs) noexcept
{ return static_cast<unsigned>(__lhs) == static_cast<unsigned>(__rhs); }

inline constexpr
bool operator!=(const day& __lhs, const day& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
bool operator< (const day& __lhs, const day& __rhs) noexcept
{ return static_cast<unsigned>(__lhs) <  static_cast<unsigned>(__rhs); }

inline constexpr
bool operator> (const day& __lhs, const day& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const day& __lhs, const day& __rhs) noexcept
{ return !(__rhs < __lhs);}

inline constexpr
bool operator>=(const day& __lhs, const day& __rhs) noexcept
{ return !(__lhs < __rhs); }

inline constexpr
day operator+ (const day& __lhs, const days& __rhs) noexcept
{ return day(static_cast<unsigned>(__lhs) + __rhs.count()); }

inline constexpr
day operator+ (const days& __lhs, const day& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
day operator- (const day& __lhs, const days& __rhs) noexcept
{ return __lhs + -__rhs; }

inline constexpr
days operator-(const day& __lhs, const day& __rhs) noexcept
{ return days(static_cast<int>(static_cast<unsigned>(__lhs)) -
              static_cast<int>(static_cast<unsigned>(__rhs))); }

inline constexpr day& day::operator+=(const days& __dd) noexcept
{ *this = *this + __dd; return *this; }

inline constexpr day& day::operator-=(const days& __dd) noexcept
{ *this = *this - __dd; return *this; }


class month {
private:
    unsigned char __m;
public:
    month() = default;
    explicit inline constexpr month(unsigned __val) noexcept : __m(static_cast<unsigned char>(__val)) {}
    inline constexpr month& operator++()    noexcept { ++__m; return *this; }
    inline constexpr month  operator++(int) noexcept { month __tmp = *this; ++(*this); return __tmp; }
    inline constexpr month& operator--()    noexcept { --__m; return *this; }
    inline constexpr month  operator--(int) noexcept { month __tmp = *this; --(*this); return __tmp; }
           constexpr month& operator+=(const months& __m1) noexcept;
           constexpr month& operator-=(const months& __m1) noexcept;
    explicit inline constexpr operator unsigned() const noexcept { return __m; }
    inline constexpr bool ok() const noexcept { return __m >= 1 && __m <= 12; }
};


inline constexpr
bool operator==(const month& __lhs, const month& __rhs) noexcept
{ return static_cast<unsigned>(__lhs) == static_cast<unsigned>(__rhs); }

inline constexpr
bool operator!=(const month& __lhs, const month& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
bool operator< (const month& __lhs, const month& __rhs) noexcept
{ return static_cast<unsigned>(__lhs)  < static_cast<unsigned>(__rhs); }

inline constexpr
bool operator> (const month& __lhs, const month& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const month& __lhs, const month& __rhs) noexcept
{ return !(__rhs < __lhs); }

inline constexpr
bool operator>=(const month& __lhs, const month& __rhs) noexcept
{ return !(__lhs < __rhs); }

inline constexpr
month operator+ (const month& __lhs, const months& __rhs) noexcept
{
    auto const __mu = static_cast<long long>(static_cast<unsigned>(__lhs)) + (__rhs.count() - 1);
    auto const __yr = (__mu >= 0 ? __mu : __mu - 11) / 12;
    return month{static_cast<unsigned>(__mu - __yr * 12 + 1)};
}

inline constexpr
month operator+ (const months& __lhs, const month& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
month operator- (const month& __lhs, const months& __rhs) noexcept
{ return __lhs + -__rhs; }

inline constexpr
months operator-(const month& __lhs, const month& __rhs) noexcept
{
    auto const __dm = static_cast<unsigned>(__lhs) - static_cast<unsigned>(__rhs);
    return months(__dm <= 11 ? __dm : __dm + 12);
}

inline constexpr month& month::operator+=(const months& __dm) noexcept
{ *this = *this + __dm; return *this; }

inline constexpr month& month::operator-=(const months& __dm) noexcept
{ *this = *this - __dm; return *this; }


class year {
private:
    short __y;
public:
    year() = default;
    explicit inline constexpr year(int __val) noexcept : __y(static_cast<short>(__val)) {}

    inline constexpr year& operator++()    noexcept { ++__y; return *this; }
    inline constexpr year  operator++(int) noexcept { year __tmp = *this; ++(*this); return __tmp; }
    inline constexpr year& operator--()    noexcept { --__y; return *this; }
    inline constexpr year  operator--(int) noexcept { year __tmp = *this; --(*this); return __tmp; }
           constexpr year& operator+=(const years& __dy) noexcept;
           constexpr year& operator-=(const years& __dy) noexcept;
    inline constexpr year operator+() const noexcept { return *this; }
    inline constexpr year operator-() const noexcept { return year{-__y}; }

    inline constexpr bool is_leap() const noexcept { return __y % 4 == 0 && (__y % 100 != 0 || __y % 400 == 0); }
    explicit inline constexpr operator int() const noexcept { return __y; }
           constexpr bool ok() const noexcept;
    static inline constexpr year min() noexcept { return year{-32767}; }
    static inline constexpr year max() noexcept { return year{ 32767}; }
};


inline constexpr
bool operator==(const year& __lhs, const year& __rhs) noexcept
{ return static_cast<int>(__lhs) == static_cast<int>(__rhs); }

inline constexpr
bool operator!=(const year& __lhs, const year& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
bool operator< (const year& __lhs, const year& __rhs) noexcept
{ return static_cast<int>(__lhs)  < static_cast<int>(__rhs); }

inline constexpr
bool operator> (const year& __lhs, const year& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const year& __lhs, const year& __rhs) noexcept
{ return !(__rhs < __lhs); }

inline constexpr
bool operator>=(const year& __lhs, const year& __rhs) noexcept
{ return !(__lhs < __rhs); }

inline constexpr
year operator+ (const year& __lhs, const years& __rhs) noexcept
{ return year(static_cast<int>(__lhs) + __rhs.count()); }

inline constexpr
year operator+ (const years& __lhs, const year& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year operator- (const year& __lhs, const years& __rhs) noexcept
{ return __lhs + -__rhs; }

inline constexpr
years operator-(const year& __lhs, const year& __rhs) noexcept
{ return years{static_cast<int>(__lhs) - static_cast<int>(__rhs)}; }


inline constexpr year& year::operator+=(const years& __dy) noexcept
{ *this = *this + __dy; return *this; }

inline constexpr year& year::operator-=(const years& __dy) noexcept
{ *this = *this - __dy; return *this; }

inline constexpr bool year::ok() const noexcept
{ return static_cast<int>(min()) <= __y && __y <= static_cast<int>(max()); }

class weekday_indexed;
class weekday_last;

class weekday {
private:
    unsigned char __wd;
public:
  weekday() = default;
  inline explicit constexpr weekday(unsigned __val) noexcept : __wd(static_cast<unsigned char>(__val)) {}
  inline constexpr          weekday(const sys_days& __sysd) noexcept
          : __wd(__weekday_from_days(__sysd.time_since_epoch().count())) {}
  inline explicit constexpr weekday(const local_days& __locd) noexcept
          : __wd(__weekday_from_days(__locd.time_since_epoch().count())) {}

  inline constexpr weekday& operator++()    noexcept { __wd = (__wd == 6 ? 0 : __wd + 1); return *this; }
  inline constexpr weekday  operator++(int) noexcept { weekday __tmp = *this; ++(*this); return __tmp; }
  inline constexpr weekday& operator--()    noexcept { __wd = (__wd == 0 ? 6 : __wd - 1); return *this; }
  inline constexpr weekday  operator--(int) noexcept { weekday __tmp = *this; --(*this); return __tmp; }
         constexpr weekday& operator+=(const days& __dd) noexcept;
         constexpr weekday& operator-=(const days& __dd) noexcept;
  inline explicit constexpr operator unsigned() const noexcept { return __wd; }
  inline constexpr bool ok() const noexcept { return __wd <= 6; }
         constexpr weekday_indexed operator[](unsigned __index) const noexcept;
         constexpr weekday_last    operator[](last_spec) const noexcept;

  static constexpr unsigned char __weekday_from_days(int __days) noexcept;
};


// https://howardhinnant.github.io/date_algorithms.html#weekday_from_days
inline constexpr
unsigned char weekday::__weekday_from_days(int __days) noexcept
{
    return static_cast<unsigned char>(
              static_cast<unsigned>(__days >= -4 ? (__days+4) % 7 : (__days+5) % 7 + 6)
           );
}

inline constexpr
bool operator==(const weekday& __lhs, const weekday& __rhs) noexcept
{ return static_cast<unsigned>(__lhs) == static_cast<unsigned>(__rhs); }

inline constexpr
bool operator!=(const weekday& __lhs, const weekday& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
bool operator< (const weekday& __lhs, const weekday& __rhs) noexcept
{ return static_cast<unsigned>(__lhs) <  static_cast<unsigned>(__rhs); }

inline constexpr
bool operator> (const weekday& __lhs, const weekday& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const weekday& __lhs, const weekday& __rhs) noexcept
{ return !(__rhs < __lhs);}

inline constexpr
bool operator>=(const weekday& __lhs, const weekday& __rhs) noexcept
{ return !(__lhs < __rhs); }

constexpr weekday operator+(const weekday& __lhs, const days& __rhs) noexcept
{
    auto const __mu = static_cast<long long>(static_cast<unsigned>(__lhs)) + __rhs.count();
    auto const __yr = (__mu >= 0 ? __mu : __mu - 6) / 7;
    return weekday{static_cast<unsigned>(__mu - __yr * 7)};
}

constexpr weekday operator+(const days& __lhs, const weekday& __rhs) noexcept
{ return __rhs + __lhs; }

constexpr weekday operator-(const weekday& __lhs, const days& __rhs) noexcept
{ return __lhs + -__rhs; }

constexpr days operator-(const weekday& __lhs, const weekday& __rhs) noexcept
{
    const int __wdu = static_cast<unsigned>(__lhs) - static_cast<unsigned>(__rhs);
    const int __wk = (__wdu >= 0 ? __wdu : __wdu-6) / 7;
    return days{__wdu - __wk * 7};
}

inline constexpr weekday& weekday::operator+=(const days& __dd) noexcept
{ *this = *this + __dd; return *this; }

inline constexpr weekday& weekday::operator-=(const days& __dd) noexcept
{ *this = *this - __dd; return *this; }


class weekday_indexed {
private:
    _VSTD::chrono::weekday __wd;
    unsigned char          __idx;
public:
    weekday_indexed() = default;
    inline constexpr weekday_indexed(const _VSTD::chrono::weekday& __wdval, unsigned __idxval) noexcept
        : __wd{__wdval}, __idx(__idxval) {}
    inline constexpr _VSTD::chrono::weekday weekday() const noexcept { return __wd; }
    inline constexpr unsigned                 index() const noexcept { return __idx; }
    inline constexpr bool ok() const noexcept { return __wd.ok() && __idx >= 1 && __idx <= 5; }
};

inline constexpr
bool operator==(const weekday_indexed& __lhs, const weekday_indexed& __rhs) noexcept
{ return __lhs.weekday() == __rhs.weekday() && __lhs.index() == __rhs.index(); }

inline constexpr
bool operator!=(const weekday_indexed& __lhs, const weekday_indexed& __rhs) noexcept
{ return !(__lhs == __rhs); }


class weekday_last {
private:
    _VSTD::chrono::weekday __wd;
public:
    explicit constexpr weekday_last(const _VSTD::chrono::weekday& __val) noexcept
        : __wd{__val} {}
    constexpr _VSTD::chrono::weekday weekday() const noexcept { return __wd; }
    constexpr bool ok() const noexcept { return __wd.ok(); }
};

inline constexpr
bool operator==(const weekday_last& __lhs, const weekday_last& __rhs) noexcept
{ return __lhs.weekday() == __rhs.weekday(); }

inline constexpr
bool operator!=(const weekday_last& __lhs, const weekday_last& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
weekday_indexed weekday::operator[](unsigned __index) const noexcept { return weekday_indexed{*this, __index}; }

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


inline constexpr last_spec last{};
inline constexpr weekday   Sunday{0};
inline constexpr weekday   Monday{1};
inline constexpr weekday   Tuesday{2};
inline constexpr weekday   Wednesday{3};
inline constexpr weekday   Thursday{4};
inline constexpr weekday   Friday{5};
inline constexpr weekday   Saturday{6};

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


class month_day {
private:
   chrono::month __m;
   chrono::day   __d;
public:
    month_day() = default;
    constexpr month_day(const chrono::month& __mval, const chrono::day& __dval) noexcept
        : __m{__mval}, __d{__dval} {}
    inline constexpr chrono::month month() const noexcept { return __m; }
    inline constexpr chrono::day   day()   const noexcept { return __d; }
    constexpr bool ok() const noexcept;
};

inline constexpr
bool month_day::ok() const noexcept
{
    if (!__m.ok()) return false;
    const unsigned __dval = static_cast<unsigned>(__d);
    if (__dval < 1 || __dval > 31) return false;
    if (__dval <= 29) return true;
//  Now we've got either 30 or 31
    const unsigned __mval = static_cast<unsigned>(__m);
    if (__mval == 2) return false;
    if (__mval == 4 || __mval == 6 || __mval == 9 || __mval == 11)
        return __dval == 30;
    return true;
}

inline constexpr
bool operator==(const month_day& __lhs, const month_day& __rhs) noexcept
{ return __lhs.month() == __rhs.month() && __lhs.day() == __rhs.day(); }

inline constexpr
bool operator!=(const month_day& __lhs, const month_day& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
month_day operator/(const month& __lhs, const day& __rhs) noexcept
{ return month_day{__lhs, __rhs}; }

constexpr
month_day operator/(const day& __lhs, const month& __rhs) noexcept
{ return __rhs / __lhs; }

inline constexpr
month_day operator/(const month& __lhs, int __rhs) noexcept
{ return __lhs / day(__rhs); }

constexpr
month_day operator/(int __lhs, const day& __rhs) noexcept
{ return month(__lhs) / __rhs; }

constexpr
month_day operator/(const day& __lhs, int __rhs) noexcept
{ return month(__rhs) / __lhs; }


inline constexpr
bool operator< (const month_day& __lhs, const month_day& __rhs) noexcept
{ return __lhs.month() != __rhs.month() ? __lhs.month() < __rhs.month() : __lhs.day() < __rhs.day(); }

inline constexpr
bool operator> (const month_day& __lhs, const month_day& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const month_day& __lhs, const month_day& __rhs) noexcept
{ return !(__rhs < __lhs);}

inline constexpr
bool operator>=(const month_day& __lhs, const month_day& __rhs) noexcept
{ return !(__lhs < __rhs); }



class month_day_last {
private:
    chrono::month __m;
public:
    explicit constexpr month_day_last(const chrono::month& __val) noexcept
        : __m{__val} {}
    inline constexpr chrono::month month() const noexcept { return __m; }
    inline constexpr bool ok() const noexcept { return __m.ok(); }
};

inline constexpr
bool operator==(const month_day_last& __lhs, const month_day_last& __rhs) noexcept
{ return __lhs.month() == __rhs.month(); }

inline constexpr
bool operator!=(const month_day_last& __lhs, const month_day_last& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
bool operator< (const month_day_last& __lhs, const month_day_last& __rhs) noexcept
{ return __lhs.month() < __rhs.month(); }

inline constexpr
bool operator> (const month_day_last& __lhs, const month_day_last& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const month_day_last& __lhs, const month_day_last& __rhs) noexcept
{ return !(__rhs < __lhs);}

inline constexpr
bool operator>=(const month_day_last& __lhs, const month_day_last& __rhs) noexcept
{ return !(__lhs < __rhs); }

inline constexpr
month_day_last operator/(const month& __lhs, last_spec) noexcept
{ return month_day_last{__lhs}; }

inline constexpr
month_day_last operator/(last_spec, const month& __rhs) noexcept
{ return month_day_last{__rhs}; }

inline constexpr
month_day_last operator/(int __lhs, last_spec) noexcept
{ return month_day_last{month(__lhs)}; }

inline constexpr
month_day_last operator/(last_spec, int __rhs) noexcept
{ return month_day_last{month(__rhs)}; }


class month_weekday {
private:
    chrono::month __m;
    chrono::weekday_indexed __wdi;
public:
    month_weekday() = default;
    constexpr month_weekday(const chrono::month& __mval, const chrono::weekday_indexed& __wdival) noexcept
        : __m{__mval}, __wdi{__wdival} {}
    inline constexpr chrono::month                     month() const noexcept { return __m; }
    inline constexpr chrono::weekday_indexed weekday_indexed() const noexcept { return __wdi; }
    inline constexpr bool                                 ok() const noexcept { return __m.ok() && __wdi.ok(); }
};

inline constexpr
bool operator==(const month_weekday& __lhs, const month_weekday& __rhs) noexcept
{ return __lhs.month() == __rhs.month() && __lhs.weekday_indexed() == __rhs.weekday_indexed(); }

inline constexpr
bool operator!=(const month_weekday& __lhs, const month_weekday& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
month_weekday operator/(const month& __lhs, const weekday_indexed& __rhs) noexcept
{ return month_weekday{__lhs, __rhs}; }

inline constexpr
month_weekday operator/(int __lhs, const weekday_indexed& __rhs) noexcept
{ return month_weekday{month(__lhs), __rhs}; }

inline constexpr
month_weekday operator/(const weekday_indexed& __lhs, const month& __rhs) noexcept
{ return month_weekday{__rhs, __lhs}; }

inline constexpr
month_weekday operator/(const weekday_indexed& __lhs, int __rhs) noexcept
{ return month_weekday{month(__rhs), __lhs}; }


class month_weekday_last {
    chrono::month        __m;
    chrono::weekday_last __wdl;
  public:
    constexpr month_weekday_last(const chrono::month& __mval, const chrono::weekday_last& __wdlval) noexcept
        : __m{__mval}, __wdl{__wdlval} {}
    inline constexpr chrono::month               month() const noexcept { return __m; }
    inline constexpr chrono::weekday_last weekday_last() const noexcept { return __wdl; }
    inline constexpr bool                           ok() const noexcept { return __m.ok() && __wdl.ok(); }
};

inline constexpr
bool operator==(const month_weekday_last& __lhs, const month_weekday_last& __rhs) noexcept
{ return __lhs.month() == __rhs.month() && __lhs.weekday_last() == __rhs.weekday_last(); }

inline constexpr
bool operator!=(const month_weekday_last& __lhs, const month_weekday_last& __rhs) noexcept
{ return !(__lhs == __rhs); }


inline constexpr
month_weekday_last operator/(const month& __lhs, const weekday_last& __rhs) noexcept
{ return month_weekday_last{__lhs, __rhs}; }

inline constexpr
month_weekday_last operator/(int __lhs, const weekday_last& __rhs) noexcept
{ return month_weekday_last{month(__lhs), __rhs}; }

inline constexpr
month_weekday_last operator/(const weekday_last& __lhs, const month& __rhs) noexcept
{ return month_weekday_last{__rhs, __lhs}; }

inline constexpr
month_weekday_last operator/(const weekday_last& __lhs, int __rhs) noexcept
{ return month_weekday_last{month(__rhs), __lhs}; }


class year_month {
    chrono::year  __y;
    chrono::month __m;
public:
    year_month() = default;
    constexpr year_month(const chrono::year& __yval, const chrono::month& __mval) noexcept
        : __y{__yval}, __m{__mval} {}
    inline constexpr chrono::year  year()  const noexcept { return __y; }
    inline constexpr chrono::month month() const noexcept { return __m; }
    inline constexpr year_month& operator+=(const months& __dm) noexcept { this->__m += __dm; return *this; }
    inline constexpr year_month& operator-=(const months& __dm) noexcept { this->__m -= __dm; return *this; }
    inline constexpr year_month& operator+=(const years& __dy)  noexcept { this->__y += __dy; return *this; }
    inline constexpr year_month& operator-=(const years& __dy)  noexcept { this->__y -= __dy; return *this; }
    inline constexpr bool ok() const noexcept { return __y.ok() && __m.ok(); }
};

inline constexpr
year_month operator/(const year& __y, const month& __m) noexcept { return year_month{__y, __m}; }

inline constexpr
year_month operator/(const year& __y, int __m) noexcept { return year_month{__y, month(__m)}; }

inline constexpr
bool operator==(const year_month& __lhs, const year_month& __rhs) noexcept
{ return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month(); }

inline constexpr
bool operator!=(const year_month& __lhs, const year_month& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
bool operator< (const year_month& __lhs, const year_month& __rhs) noexcept
{ return __lhs.year() != __rhs.year() ? __lhs.year() < __rhs.year() : __lhs.month() < __rhs.month(); }

inline constexpr
bool operator> (const year_month& __lhs, const year_month& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const year_month& __lhs, const year_month& __rhs) noexcept
{ return !(__rhs < __lhs);}

inline constexpr
bool operator>=(const year_month& __lhs, const year_month& __rhs) noexcept
{ return !(__lhs < __rhs); }

constexpr year_month operator+(const year_month& __lhs, const months& __rhs) noexcept
{
    int __dmi = static_cast<int>(static_cast<unsigned>(__lhs.month())) - 1 + __rhs.count();
    const int __dy = (__dmi >= 0 ? __dmi : __dmi-11) / 12;
    __dmi = __dmi - __dy * 12 + 1;
    return (__lhs.year() + years(__dy)) / month(static_cast<unsigned>(__dmi));
}

constexpr year_month operator+(const months& __lhs, const year_month& __rhs) noexcept
{ return __rhs + __lhs; }

constexpr year_month operator+(const year_month& __lhs, const years& __rhs) noexcept
{ return (__lhs.year() + __rhs) / __lhs.month(); }

constexpr year_month operator+(const years& __lhs, const year_month& __rhs) noexcept
{ return __rhs + __lhs; }

constexpr months     operator-(const year_month& __lhs, const year_month& __rhs) noexcept
{ return (__lhs.year() - __rhs.year()) + months(static_cast<unsigned>(__lhs.month()) - static_cast<unsigned>(__rhs.month())); }

constexpr year_month operator-(const year_month& __lhs, const months& __rhs) noexcept
{ return __lhs + -__rhs; }

constexpr year_month operator-(const year_month& __lhs, const years& __rhs) noexcept
{ return __lhs + -__rhs; }

class year_month_day_last;

class year_month_day {
private:
    chrono::year  __y;
    chrono::month __m;
    chrono::day   __d;
public:
     year_month_day() = default;
     inline constexpr year_month_day(
            const chrono::year& __yval, const chrono::month& __mval, const chrono::day& __dval) noexcept
            : __y{__yval}, __m{__mval}, __d{__dval} {}
            constexpr year_month_day(const year_month_day_last& __ymdl) noexcept;
     inline constexpr year_month_day(const sys_days& __sysd) noexcept
            : year_month_day(__from_days(__sysd.time_since_epoch())) {}
     inline explicit constexpr year_month_day(const local_days& __locd) noexcept
            : year_month_day(__from_days(__locd.time_since_epoch())) {}

            constexpr year_month_day& operator+=(const months& __dm) noexcept;
            constexpr year_month_day& operator-=(const months& __dm) noexcept;
            constexpr year_month_day& operator+=(const years& __dy)  noexcept;
            constexpr year_month_day& operator-=(const years& __dy)  noexcept;

     inline constexpr chrono::year   year() const noexcept { return __y; }
     inline constexpr chrono::month month() const noexcept { return __m; }
     inline constexpr chrono::day     day() const noexcept { return __d; }
     inline constexpr operator   sys_days() const noexcept          { return   sys_days{__to_days()}; }
     inline explicit constexpr operator local_days() const noexcept { return local_days{__to_days()}; }

            constexpr bool             ok() const noexcept;

     static constexpr year_month_day __from_days(days __d) noexcept;
     constexpr days __to_days() const noexcept;
};


// https://howardhinnant.github.io/date_algorithms.html#civil_from_days
inline constexpr
year_month_day
year_month_day::__from_days(days __d) noexcept
{
    static_assert(std::numeric_limits<unsigned>::digits >= 18, "");
    static_assert(std::numeric_limits<int>::digits >= 20     , "");
    const int      __z = __d.count() + 719468;
    const int      __era = (__z >= 0 ? __z : __z - 146096) / 146097;
    const unsigned __doe = static_cast<unsigned>(__z - __era * 146097);              // [0, 146096]
    const unsigned __yoe = (__doe - __doe/1460 + __doe/36524 - __doe/146096) / 365;  // [0, 399]
    const int      __yr = static_cast<int>(__yoe) + __era * 400;
    const unsigned __doy = __doe - (365 * __yoe + __yoe/4 - __yoe/100);              // [0, 365]
    const unsigned __mp = (5 * __doy + 2)/153;                                       // [0, 11]
    const unsigned __dy = __doy - (153 * __mp + 2)/5 + 1;                            // [1, 31]
    const unsigned __mth = __mp + (__mp < 10 ? 3 : -9);                              // [1, 12]
    return year_month_day{chrono::year{__yr + (__mth <= 2)}, chrono::month{__mth}, chrono::day{__dy}};
}

// https://howardhinnant.github.io/date_algorithms.html#days_from_civil
inline constexpr days year_month_day::__to_days() const noexcept
{
    static_assert(std::numeric_limits<unsigned>::digits >= 18, "");
    static_assert(std::numeric_limits<int>::digits >= 20     , "");

    const int      __yr  = static_cast<int>(__y) - (__m <= February);
    const unsigned __mth = static_cast<unsigned>(__m);
    const unsigned __dy  = static_cast<unsigned>(__d);

    const int      __era = (__yr >= 0 ? __yr : __yr - 399) / 400;
    const unsigned __yoe = static_cast<unsigned>(__yr - __era * 400);                // [0, 399]
    const unsigned __doy = (153 * (__mth + (__mth > 2 ? -3 : 9)) + 2) / 5 + __dy-1;  // [0, 365]
    const unsigned __doe = __yoe * 365 + __yoe/4 - __yoe/100 + __doy;                // [0, 146096]
    return days{__era * 146097 + static_cast<int>(__doe) - 719468};
}

inline constexpr
bool operator==(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
{ return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.day() == __rhs.day(); }

inline constexpr
bool operator!=(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
bool operator< (const year_month_day& __lhs, const year_month_day& __rhs) noexcept
{
    if (__lhs.year() < __rhs.year()) return true;
    if (__lhs.year() > __rhs.year()) return false;
    if (__lhs.month() < __rhs.month()) return true;
    if (__lhs.month() > __rhs.month()) return false;
    return __lhs.day() < __rhs.day();
}

inline constexpr
bool operator> (const year_month_day& __lhs, const year_month_day& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
{ return !(__rhs < __lhs);}

inline constexpr
bool operator>=(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
{ return !(__lhs < __rhs); }

inline constexpr
year_month_day operator/(const year_month& __lhs, const day& __rhs) noexcept
{ return year_month_day{__lhs.year(), __lhs.month(), __rhs}; }

inline constexpr
year_month_day operator/(const year_month& __lhs, int __rhs) noexcept
{ return __lhs / day(__rhs); }

inline constexpr
year_month_day operator/(const year& __lhs, const month_day& __rhs) noexcept
{ return __lhs / __rhs.month() / __rhs.day(); }

inline constexpr
year_month_day operator/(int __lhs, const month_day& __rhs) noexcept
{ return year(__lhs) / __rhs; }

inline constexpr
year_month_day operator/(const month_day& __lhs, const year& __rhs) noexcept
{ return __rhs / __lhs; }

inline constexpr
year_month_day operator/(const month_day& __lhs, int __rhs) noexcept
{ return year(__rhs) / __lhs; }


inline constexpr
year_month_day operator+(const year_month_day& __lhs, const months& __rhs) noexcept
{ return (__lhs.year()/__lhs.month() + __rhs)/__lhs.day(); }

inline constexpr
year_month_day operator+(const months& __lhs, const year_month_day& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year_month_day operator-(const year_month_day& __lhs, const months& __rhs) noexcept
{ return __lhs + -__rhs; }

inline constexpr
year_month_day operator+(const year_month_day& __lhs, const years& __rhs) noexcept
{ return (__lhs.year() + __rhs) / __lhs.month() / __lhs.day(); }

inline constexpr
year_month_day operator+(const years& __lhs, const year_month_day& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year_month_day operator-(const year_month_day& __lhs, const years& __rhs) noexcept
{ return __lhs + -__rhs; }

inline constexpr year_month_day& year_month_day::operator+=(const months& __dm) noexcept { *this = *this + __dm; return *this; }
inline constexpr year_month_day& year_month_day::operator-=(const months& __dm) noexcept { *this = *this - __dm; return *this; }
inline constexpr year_month_day& year_month_day::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
inline constexpr year_month_day& year_month_day::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }

class year_month_day_last {
private:
    chrono::year           __y;
    chrono::month_day_last __mdl;
public:
     constexpr year_month_day_last(const year& __yval, const month_day_last& __mdlval) noexcept
        : __y{__yval}, __mdl{__mdlval} {}

     constexpr year_month_day_last& operator+=(const months& __m) noexcept;
     constexpr year_month_day_last& operator-=(const months& __m) noexcept;
     constexpr year_month_day_last& operator+=(const years& __y)  noexcept;
     constexpr year_month_day_last& operator-=(const years& __y)  noexcept;

     inline constexpr chrono::year                     year() const noexcept { return __y; }
     inline constexpr chrono::month                   month() const noexcept { return __mdl.month(); }
     inline constexpr chrono::month_day_last month_day_last() const noexcept { return __mdl; }
            constexpr chrono::day                       day() const noexcept;
     inline constexpr operator                     sys_days() const noexcept { return   sys_days{year()/month()/day()}; }
     inline explicit constexpr operator          local_days() const noexcept { return local_days{year()/month()/day()}; }
     inline constexpr bool                               ok() const noexcept { return __y.ok() && __mdl.ok(); }
};

inline constexpr
chrono::day year_month_day_last::day() const noexcept
{
    constexpr chrono::day __d[] =
    {
        chrono::day(31), chrono::day(28), chrono::day(31),
        chrono::day(30), chrono::day(31), chrono::day(30),
        chrono::day(31), chrono::day(31), chrono::day(30),
        chrono::day(31), chrono::day(30), chrono::day(31)
    };
    return month() != February || !__y.is_leap() ?
        __d[static_cast<unsigned>(month()) - 1] : chrono::day{29};
}

inline constexpr
bool operator==(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
{ return __lhs.year() == __rhs.year() && __lhs.month_day_last() == __rhs.month_day_last(); }

inline constexpr
bool operator!=(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
bool operator< (const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
{
    if (__lhs.year() < __rhs.year()) return true;
    if (__lhs.year() > __rhs.year()) return false;
    return __lhs.month_day_last() < __rhs.month_day_last();
}

inline constexpr
bool operator> (const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
{ return __rhs < __lhs; }

inline constexpr
bool operator<=(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
{ return !(__rhs < __lhs);}

inline constexpr
bool operator>=(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
{ return !(__lhs < __rhs); }

inline constexpr year_month_day_last operator/(const year_month& __lhs, last_spec) noexcept
{ return year_month_day_last{__lhs.year(), month_day_last{__lhs.month()}}; }

inline constexpr year_month_day_last operator/(const year& __lhs, const month_day_last& __rhs) noexcept
{ return year_month_day_last{__lhs, __rhs}; }

inline constexpr year_month_day_last operator/(int __lhs, const month_day_last& __rhs) noexcept
{ return year_month_day_last{year{__lhs}, __rhs}; }

inline constexpr year_month_day_last operator/(const month_day_last& __lhs, const year& __rhs) noexcept
{ return __rhs / __lhs; }

inline constexpr year_month_day_last operator/(const month_day_last& __lhs, int __rhs) noexcept
{ return year{__rhs} / __lhs; }


inline constexpr
year_month_day_last operator+(const year_month_day_last& __lhs, const months& __rhs) noexcept
{ return (__lhs.year() / __lhs.month() + __rhs) / last; }

inline constexpr
year_month_day_last operator+(const months& __lhs, const year_month_day_last& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year_month_day_last operator-(const year_month_day_last& __lhs, const months& __rhs) noexcept
{ return __lhs + (-__rhs); }

inline constexpr
year_month_day_last operator+(const year_month_day_last& __lhs, const years& __rhs) noexcept
{ return year_month_day_last{__lhs.year() + __rhs, __lhs.month_day_last()}; }

inline constexpr
year_month_day_last operator+(const years& __lhs, const year_month_day_last& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year_month_day_last operator-(const year_month_day_last& __lhs, const years& __rhs) noexcept
{ return __lhs + (-__rhs); }

inline constexpr year_month_day_last& year_month_day_last::operator+=(const months& __dm) noexcept { *this = *this + __dm; return *this; }
inline constexpr year_month_day_last& year_month_day_last::operator-=(const months& __dm) noexcept { *this = *this - __dm; return *this; }
inline constexpr year_month_day_last& year_month_day_last::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
inline constexpr year_month_day_last& year_month_day_last::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }

inline constexpr year_month_day::year_month_day(const year_month_day_last& __ymdl) noexcept
    : __y{__ymdl.year()}, __m{__ymdl.month()}, __d{__ymdl.day()} {}

inline constexpr bool year_month_day::ok() const noexcept
{
    if (!__y.ok() || !__m.ok()) return false;
    return chrono::day{1} <= __d && __d <= (__y / __m / last).day();
}

class year_month_weekday {
    chrono::year            __y;
    chrono::month           __m;
    chrono::weekday_indexed __wdi;
public:
    year_month_weekday() = default;
    constexpr year_month_weekday(const chrono::year& __yval, const chrono::month& __mval,
                               const chrono::weekday_indexed& __wdival) noexcept
        : __y{__yval}, __m{__mval}, __wdi{__wdival} {}
    constexpr year_month_weekday(const sys_days& __sysd) noexcept
            : year_month_weekday(__from_days(__sysd.time_since_epoch())) {}
    inline explicit constexpr year_month_weekday(const local_days& __locd) noexcept
            : year_month_weekday(__from_days(__locd.time_since_epoch())) {}
    constexpr year_month_weekday& operator+=(const months& m) noexcept;
    constexpr year_month_weekday& operator-=(const months& m) noexcept;
    constexpr year_month_weekday& operator+=(const years& y)  noexcept;
    constexpr year_month_weekday& operator-=(const years& y)  noexcept;

    inline constexpr chrono::year                       year() const noexcept { return __y; }
    inline constexpr chrono::month                     month() const noexcept { return __m; }
    inline constexpr chrono::weekday                 weekday() const noexcept { return __wdi.weekday(); }
    inline constexpr unsigned                          index() const noexcept { return __wdi.index(); }
    inline constexpr chrono::weekday_indexed weekday_indexed() const noexcept { return __wdi; }

    inline constexpr                       operator sys_days() const noexcept { return   sys_days{__to_days()}; }
    inline explicit constexpr operator            local_days() const noexcept { return local_days{__to_days()}; }
    inline constexpr bool ok() const noexcept
    {
        if (!__y.ok() || !__m.ok() || !__wdi.ok()) return false;
    //  TODO: make sure it's a valid date
        return true;
    }

    static constexpr year_month_weekday __from_days(days __d) noexcept;
    constexpr days __to_days() const noexcept;
};

inline constexpr
year_month_weekday year_month_weekday::__from_days(days __d) noexcept
{
    const sys_days      __sysd{__d};
    const chrono::weekday __wd = chrono::weekday(__sysd);
    const year_month_day __ymd = year_month_day(__sysd);
    return year_month_weekday{__ymd.year(), __ymd.month(),
                              __wd[(static_cast<unsigned>(__ymd.day())-1)/7+1]};
}

inline constexpr
days year_month_weekday::__to_days() const noexcept
{
    const sys_days __sysd = sys_days(__y/__m/1);
    return (__sysd + (__wdi.weekday() - chrono::weekday(__sysd) + days{(__wdi.index()-1)*7}))
                .time_since_epoch();
}

inline constexpr
bool operator==(const year_month_weekday& __lhs, const year_month_weekday& __rhs) noexcept
{ return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.weekday_indexed() == __rhs.weekday_indexed(); }

inline constexpr
bool operator!=(const year_month_weekday& __lhs, const year_month_weekday& __rhs) noexcept
{ return !(__lhs == __rhs); }

inline constexpr
year_month_weekday operator/(const year_month& __lhs, const weekday_indexed& __rhs) noexcept
{ return year_month_weekday{__lhs.year(), __lhs.month(), __rhs}; }

inline constexpr
year_month_weekday operator/(const year& __lhs, const month_weekday& __rhs) noexcept
{ return year_month_weekday{__lhs, __rhs.month(), __rhs.weekday_indexed()}; }

inline constexpr
year_month_weekday operator/(int __lhs, const month_weekday& __rhs) noexcept
{ return year(__lhs) / __rhs; }

inline constexpr
year_month_weekday operator/(const month_weekday& __lhs, const year& __rhs) noexcept
{ return __rhs / __lhs; }

inline constexpr
year_month_weekday operator/(const month_weekday& __lhs, int __rhs) noexcept
{ return year(__rhs) / __lhs; }


inline constexpr
year_month_weekday operator+(const year_month_weekday& __lhs, const months& __rhs) noexcept
{ return (__lhs.year() / __lhs.month() + __rhs) / __lhs.weekday_indexed(); }

inline constexpr
year_month_weekday operator+(const months& __lhs, const year_month_weekday& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year_month_weekday operator-(const year_month_weekday& __lhs, const months& __rhs) noexcept
{ return __lhs + (-__rhs); }

inline constexpr
year_month_weekday operator+(const year_month_weekday& __lhs, const years& __rhs) noexcept
{ return year_month_weekday{__lhs.year() + __rhs, __lhs.month(), __lhs.weekday_indexed()}; }

inline constexpr
year_month_weekday operator+(const years& __lhs, const year_month_weekday& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year_month_weekday operator-(const year_month_weekday& __lhs, const years& __rhs) noexcept
{ return __lhs + (-__rhs); }


inline constexpr year_month_weekday& year_month_weekday::operator+=(const months& __dm) noexcept { *this = *this + __dm; return *this; }
inline constexpr year_month_weekday& year_month_weekday::operator-=(const months& __dm) noexcept { *this = *this - __dm; return *this; }
inline constexpr year_month_weekday& year_month_weekday::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
inline constexpr year_month_weekday& year_month_weekday::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }

class year_month_weekday_last {
private:
    chrono::year         __y;
    chrono::month        __m;
    chrono::weekday_last __wdl;
public:
    constexpr year_month_weekday_last(const chrono::year& __yval, const chrono::month& __mval,
                                      const chrono::weekday_last& __wdlval) noexcept
                : __y{__yval}, __m{__mval}, __wdl{__wdlval} {}
    constexpr year_month_weekday_last& operator+=(const months& __dm) noexcept;
    constexpr year_month_weekday_last& operator-=(const months& __dm) noexcept;
    constexpr year_month_weekday_last& operator+=(const years& __dy)  noexcept;
    constexpr year_month_weekday_last& operator-=(const years& __dy)  noexcept;

    inline constexpr chrono::year                 year() const noexcept { return __y; }
    inline constexpr chrono::month               month() const noexcept { return __m; }
    inline constexpr chrono::weekday           weekday() const noexcept { return __wdl.weekday(); }
    inline constexpr chrono::weekday_last weekday_last() const noexcept { return __wdl; }
    inline constexpr operator                 sys_days() const noexcept { return   sys_days{__to_days()}; }
    inline explicit constexpr operator      local_days() const noexcept { return local_days{__to_days()}; }
    inline constexpr bool ok() const noexcept { return __y.ok() && __m.ok() && __wdl.ok(); }

    constexpr days __to_days() const noexcept;

};

inline constexpr
days year_month_weekday_last::__to_days() const noexcept
{
    const sys_days __last = sys_days{__y/__m/last};
    return (__last - (chrono::weekday{__last} - __wdl.weekday())).time_since_epoch();

}

inline constexpr
bool operator==(const year_month_weekday_last& __lhs, const year_month_weekday_last& __rhs) noexcept
{ return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.weekday_last() == __rhs.weekday_last(); }

inline constexpr
bool operator!=(const year_month_weekday_last& __lhs, const year_month_weekday_last& __rhs) noexcept
{ return !(__lhs == __rhs); }


inline constexpr
year_month_weekday_last operator/(const year_month& __lhs, const weekday_last& __rhs) noexcept
{ return year_month_weekday_last{__lhs.year(), __lhs.month(), __rhs}; }

inline constexpr
year_month_weekday_last operator/(const year& __lhs, const month_weekday_last& __rhs) noexcept
{ return year_month_weekday_last{__lhs, __rhs.month(), __rhs.weekday_last()}; }

inline constexpr
year_month_weekday_last operator/(int __lhs, const month_weekday_last& __rhs) noexcept
{ return year(__lhs) / __rhs; }

inline constexpr
year_month_weekday_last operator/(const month_weekday_last& __lhs, const year& __rhs) noexcept
{ return __rhs / __lhs; }

inline constexpr
year_month_weekday_last operator/(const month_weekday_last& __lhs, int __rhs) noexcept
{ return year(__rhs) / __lhs; }


inline constexpr
year_month_weekday_last operator+(const year_month_weekday_last& __lhs, const months& __rhs) noexcept
{ return (__lhs.year() / __lhs.month() + __rhs) / __lhs.weekday_last(); }

inline constexpr
year_month_weekday_last operator+(const months& __lhs, const year_month_weekday_last& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year_month_weekday_last operator-(const year_month_weekday_last& __lhs, const months& __rhs) noexcept
{ return __lhs + (-__rhs); }

inline constexpr
year_month_weekday_last operator+(const year_month_weekday_last& __lhs, const years& __rhs) noexcept
{ return year_month_weekday_last{__lhs.year() + __rhs, __lhs.month(), __lhs.weekday_last()}; }

inline constexpr
year_month_weekday_last operator+(const years& __lhs, const year_month_weekday_last& __rhs) noexcept
{ return __rhs + __lhs; }

inline constexpr
year_month_weekday_last operator-(const year_month_weekday_last& __lhs, const years& __rhs) noexcept
{ return __lhs + (-__rhs); }

inline constexpr year_month_weekday_last& year_month_weekday_last::operator+=(const months& __dm) noexcept { *this = *this + __dm; return *this; }
inline constexpr year_month_weekday_last& year_month_weekday_last::operator-=(const months& __dm) noexcept { *this = *this - __dm; return *this; }
inline constexpr year_month_weekday_last& year_month_weekday_last::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
inline constexpr year_month_weekday_last& year_month_weekday_last::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }

#endif // _LIBCPP_STD_VER > 17
} // chrono

#if _LIBCPP_STD_VER > 11
// Suffixes for duration literals [time.duration.literals]
inline namespace literals
{
  inline namespace chrono_literals
  {

    constexpr chrono::hours operator""h(unsigned long long __h)
    {
        return chrono::hours(static_cast<chrono::hours::rep>(__h));
    }

    constexpr chrono::duration<long double, ratio<3600,1>> operator""h(long double __h)
    {
        return chrono::duration<long double, ratio<3600,1>>(__h);
    }


    constexpr chrono::minutes operator""min(unsigned long long __m)
    {
        return chrono::minutes(static_cast<chrono::minutes::rep>(__m));
    }

    constexpr chrono::duration<long double, ratio<60,1>> operator""min(long double __m)
    {
        return chrono::duration<long double, ratio<60,1>> (__m);
    }


    constexpr chrono::seconds operator""s(unsigned long long __s)
    {
        return chrono::seconds(static_cast<chrono::seconds::rep>(__s));
    }

    constexpr chrono::duration<long double> operator""s(long double __s)
    {
        return chrono::duration<long double> (__s);
    }


    constexpr chrono::milliseconds operator""ms(unsigned long long __ms)
    {
        return chrono::milliseconds(static_cast<chrono::milliseconds::rep>(__ms));
    }

    constexpr chrono::duration<long double, milli> operator""ms(long double __ms)
    {
        return chrono::duration<long double, milli>(__ms);
    }


    constexpr chrono::microseconds operator""us(unsigned long long __us)
    {
        return chrono::microseconds(static_cast<chrono::microseconds::rep>(__us));
    }

    constexpr chrono::duration<long double, micro> operator""us(long double __us)
    {
        return chrono::duration<long double, micro> (__us);
    }


    constexpr chrono::nanoseconds operator""ns(unsigned long long __ns)
    {
        return chrono::nanoseconds(static_cast<chrono::nanoseconds::rep>(__ns));
    }

    constexpr chrono::duration<long double, nano> operator""ns(long double __ns)
    {
        return chrono::duration<long double, nano> (__ns);
    }

#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CXX20_CHRONO_LITERALS)
    constexpr chrono::day operator ""d(unsigned long long __d) noexcept
    {
        return chrono::day(static_cast<unsigned>(__d));
    }

    constexpr chrono::year operator ""y(unsigned long long __y) noexcept
    {
        return chrono::year(static_cast<int>(__y));
    }
#endif
}}

namespace chrono { // hoist the literals into namespace std::chrono
   using namespace literals::chrono_literals;
}

#endif

_LIBCPP_END_NAMESPACE_STD

#ifndef _LIBCPP_CXX03_LANG
_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
struct _FilesystemClock {
#if !defined(_LIBCPP_HAS_NO_INT128)
  typedef __int128_t rep;
  typedef nano period;
#else
  typedef long long rep;
  typedef nano period;
#endif

  typedef chrono::duration<rep, period> duration;
  typedef chrono::time_point<_FilesystemClock> time_point;

  static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;

  _LIBCPP_AVAILABILITY_FILESYSTEM _LIBCPP_FUNC_VIS static time_point now() noexcept;

  _LIBCPP_INLINE_VISIBILITY
  static time_t to_time_t(const time_point& __t) noexcept {
      typedef chrono::duration<rep> __secs;
      return time_t(
          chrono::duration_cast<__secs>(__t.time_since_epoch()).count());
  }

  _LIBCPP_INLINE_VISIBILITY
  static time_point from_time_t(time_t __t) noexcept {
      typedef chrono::duration<rep> __secs;
      return time_point(__secs(__t));
  }
};
_LIBCPP_END_NAMESPACE_FILESYSTEM
#endif // !_LIBCPP_CXX03_LANG

_LIBCPP_POP_MACROS

#endif  // _LIBCPP_CHRONO