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<chrono> operators

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operator+

Addition operator for the following types:

1) 
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>& Left,
      const duration<Rep2, Period2>& Right);

2)
template <class Clock, class Duration1, class Rep2, class Period2>
constexpr time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type>
   operator+(
      const time_point<Clock, Duration1>& Time,
      const duration<Rep2, Period2>& Dur);

3)
template <class Rep1, class Period1, class Clock, class Duration2>
time_point<Clock, constexpr typename common_type<duration<Rep1, Period1>, Duration2>::type>
   operator+(
      const duration<Rep1, Period1>& Dur,
      const time_point<Clock, Duration2>& Time);

4)
constexpr day operator+(const day& d, const days& ds) noexcept; // C++20
constexpr day operator+(const days& ds, const day&  d) noexcept; // C++20

5)
constexpr month operator+(const month& m, const months& ms) noexcept; // C++20
constexpr month operator+(const months& ms, const month& m) noexcept; // C++20

6)
constexpr weekday operator+(const weekday& wd, const days& wds) noexcept // C++20
constexpr weekday operator+(const days& ds, const weekday& wd) noexcept; // C++20

7)
constexpr year operator+(const year& y, const years& ys) noexcept; // C++20
constexpr year operator+(const years& ys, const year& y) noexcept; // C++20

8)
constexpr year_month operator+(const year_month& ym, const months& dm) noexcept; // C++20
constexpr year_month operator+(const months& dm, const year_month& ym) noexcept; // C++20
constexpr year_month operator+(const year_month& ym, const years& dy) noexcept; // C++20
constexpr year_month operator+(const years& dy, const year_month& ym) noexcept; // C++20

9)
constexpr year_month_day operator+(const year_month_day& ymd, const months& dm) noexcept; // C++20
constexpr year_month_day operator+(const months& dm, const year_month_day& ymd) noexcept; // C++20
constexpr year_month_day operator+(const year_month_day& ymd, const years& dy) noexcept; // C++20
constexpr year_month_day operator+(const years& dy, const year_month_day& ymd) noexcept; // C++20

10)
constexpr year_month_day_last operator+(const year_month_day_last& ymdl, const months& dm) noexcept; // C++20

11)
constexpr year_month_day_last operator+(const months& dm, const year_month_day_last& ymdl) noexcept; // C++20

12)
constexpr year_month_day_last operator+(const year_month_day_last& ymdl, const years& dy) noexcept; // C++20
constexpr year_month_day_last operator+(const years& dy, const year_month_day_last& ymdl) noexcept; // C++20

13)
constexpr year_month_weekday operator+(const year_month_weekday& ymwd, const months& dm) noexcept; // C++20
constexpr year_month_weekday operator+(const months& dm, const year_month_weekday& ymwd) noexcept; // C++20

14)
constexpr year_month_weekday operator+(const year_month_weekday& ymwd, const years& dy) noexcept; // C++20

15)
constexpr year_month_weekday operator+(const years& dy, const year_month_weekday& ymwd) noexcept; // C++20

16)
constexpr year_month_weekday_last operator+(const year_month_weekday_last& ymwdl, const months& dm) noexcept; // C++20
constexpr year_month_weekday_last operator+(const months& dm, const year_month_weekday_last& ymwdl) noexcept; // C++20

17)
constexpr year_month_weekday_last operator+(const year_month_weekday_last& ymwdl, const years& dy) noexcept; // C++20
constexpr year_month_weekday_last operator+(const years& dy, const year_month_weekday_last& ymwdl) noexcept; // C++20

Return value

1) After converting Left and Right to their common type, returns a duration with a tick count equal to the sum of the converted tick counts.

2-3) Return a time_point object that represents a point in time that is displaced by the interval Dur from the point in time Time.

4) Returns the result of d+ds.count(). If the result is out of the range [0, 255], then the result is unspecified.

5) Returns the result of m+ms.count(). If the result is out of the range [1, 12], it's reduced modulo 12 and then +1.

6) Returns the result of adding the number of days and weekdays to the weekday. The result will be modulo 7, so always in the range [0,6]

7) Returns the result of adding the year to the specified number of years.

8) Returns the result of adding the number of months and years to the specified month and year.

9) Returns the result of adding months or years to a year_month_day. If ymd.month() is February and ymd.day() is not in the range [1d, 28d], ok() may return false for the result of the addition.

10) Returns (ymdl.year() / ymdl.month() + dm) / last. Note: The / used here isn't a division operator. It's the date operator.

11) Returns ymdl + dm.

12) Returns {ymdl.year()+dy, ymdl.month_day_last()}

13) Returns ymwd + dm.count().

14-15) Returns {ymwd.year()+dy, ymwd.month(), ymwd.weekday_indexed()}.

16) Returns (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_last(). Note: The / used here isn't a division operator but the date operator.

17) Returns: ymwdl + dy

Example: operator+

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
    // day
    day d{1};
    std::cout << d + days(2) << '\n'; // 03

    // month
    month m{11};
    std::cout << m + months(3)<< '\n'; // Feb

    // weekday
    weekday wd = Thursday;
    std::cout << wd + days(1) << '\n'; // Fri

    // year_month_day_last
    year_month_day_last ymdl{June / last / 2021};
    std::cout << ymdl + years{1} + months{1} << '\n'; // 2022/Jul/last

    // year_month_weekday
    year_month_weekday ymw{ year(1997) / January / Wednesday[1] };
    std::cout << ymw + months{1} << '\n'; // 1997/Feb/Wed[1]
    std::cout << ymw + years{1} << '\n'; // 1998/Jan/Wed[1] 

    // year_month_weekday_last
    year_month_weekday_last ymwl{ year(1997) / January / Wednesday[last] };
    std::cout << ymwl + months{ 1 } << '\n'; // 1997/Feb/Wed[last]
    std::cout << ymwl + years{ 1 } << '\n'; // 1998/Jan/Wed[last] 

    return 0;
}

03
Feb
Fri
2022/Jul/last
1997/Feb/Wed[1]
1998/Jan/Wed[1]
1997/Feb/Wed[last]
1998/Jan/Wed[last]

Unary operator+

Apply unary plus to the following types:

// duration
constexpr common_type_t<duration> operator+() const // C++20

Return value

Returns *this

operator-

Subtraction operator for the following types:

1)
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>& Left,
       const duration<Rep2, Period2>& Right);
2)
template <class Clock, class Duration1, class Rep2, class Period2>
constexpr time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type
   operator-(
       const time_point<Clock, Duration1>& Time,
       const duration<Rep2, Period2>& Dur);
3)
template <class Clock, class Duration1, class Duration2>
constexpr typename common_type<Duration1, Duration2>::type
   operator-(
       const time_point<Clock, Duration1>& Left,
       const time_point<Clock, Duration2>& Right);
4)
constexpr day operator-(const day& d,  days& ds) noexcept; // C++20
constexpr day operator-(const day& d, const day& d) noexcept; // C++20

5)
constexpr month operator-(const month& m, const months& ms) noexcept; // C++20
constexpr month operator-(const month& m, const month& ms) noexcept; // C++20

6)
constexpr months operator-(const year_month& Left, const year_month& Right) noexcept; // C++20

7)
constexpr weekday operator-(const weekday& Left, const days& Right) noexcept; // C++20

8)
constexpr days operator-(const weekday& Left, const weekday& Right) noexcept; // C++20

9)
constexpr year operator-(const year& y, const years& ys) noexcept; // C++20

10)
constexpr years operator-(const year& y, const year& y2) noexcept; // C++20

11)
constexpr year_month operator-(const year_month& ym, const months& dm) noexcept; // C++20
constexpr year_month operator-(const year_month& ym, const years& dy) noexcept; // C++20

12)
constexpr year_month_day operator-(const year_month_day& ymd, const months& dm) noexcept; // C++20
constexpr year_month_day operator-(const year_month_day& ymd, const years& dy) noexcept; // C++20

13)
constexpr year_month_day_last operator-(const year_month_day_last& ymdl, const months& dm) noexcept;  // C++20

14)
constexpr year_month_day_last operator-(const year_month_day_last& ymdl, const years& dy) noexcept;  // C++20

15)
constexpr year_month_weekday operator-(const year_month_weekday& ymwd, const months& dm) noexcept; // C++20

16)
constexpr year_month_weekday operator-(const year_month_weekday& ymwd, const years& dy) noexcept; // C++20

17)
constexpr year_month_weekday_last operator-(const year_month_weekday_last& ymwdl, const months& dm) noexcept; // C++20

18)
constexpr year_month_weekday_last operator-(const year_month_weekday_last& ymwdl, const years& dy) noexcept; // C++20

Return value

1) After converting the durations being subtracted to their common type, returns a duration with a tick count equal to the number of ticks in Right subtracted from the number of ticks in Left.

2) Returns a time_point that represents a point in time that is displaced by the negation of the time interval that is represented by Dur, from the point in time that is specified by Time.

3) Returns a duration object that represents the time interval between Left and Right.

4) Returns the result of d-ds.count(). If the result is out of the range [0, 255], then the result is unspecified.

5) If m.ok() == true and ms.ok() == true, returns the result of subtracting the two month values, or subtracting the number of months. The result will be in the range [1, 12]. If the result is negative, it wraps around. For example, subtracting one month from January (month m1{1} - months{1}; results in 12 (December).

6) Returns the difference in months between Left and Right

7) If Left.ok() == true and Right.ok() == true, returns a weekday in the range [days{0}, days{6}].

8) Returns the number of days between two weekdays.

9) Returns year(int(y)-ys.count)())

10) Returns years(int(y) - int(y2)). Subtracting two year values results in a std::chrono::years, which represents the difference in years between y and y2. For example, 2021y-2000y produces years(21).

11) Returns the result of subtracting months or years from a year_month value.

12) Returns the result of subtracting months years from a year_month_day value.

13) Returns the result of subtracting the number of months from the year_month_day_last value. Essentially: ymdl-dm.

14) Returns the result of subtracting the number of years from the year_month_day_last value. Essentially: ymdl-dy.

15) Returns the result of subtracting the number of months from the year_month_weekday value. Essentially: ymwd-dm.

16) Returns the result of subtracting the number of years from the year_month_weekday value. Essentially: ymwd-dy.

17) Returns the result of subtracting the number of months from the year_month_weekday_last value. Essentially: ymwdl-dm.

18) Returns the result of subtracting the number of years from the year_month_weekday_last value. Essentially: ymwdl-dy.

Example: operator-

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
    // day
    day d{10};
    d = d - days(5);  
    std::cout << d << '\n'; // 05

    // month 
    month m{2};
    m = m - months{1};
    std::cout << m << '\n'; // Jan
    m = m - months{1};
    std::cout << m << '\n'; // Dec

    // year
    auto diff1 = 2021y-2000y;
    auto diff2 = 2021y-years{1};
    std::cout << diff1.count() << '\n'; // 21
    std::cout << diff2 << '\n'; // 2020

    // year_month
    const year theYear{ 2021 };
    year_month ym1{theYear, June};
    year_month ym2 = ym1 - months{2};
    std::cout << ym2 << '\n'; // 2021/Apr
    year_month ym3 = ym1 - years{2};
    std::cout << ym3 << '\n'; // 2019/Jun

    // year_month_day_last
    year_month_day_last ymdl = June / last / 2021;
    std::cout << ymdl - years{1} - months{1} << '\n'; // 2022/Jul/last

    // year_month_weekday
    year_month_weekday ymw{ year(1997) / January / Wednesday[1] };
    std::cout << ymw - months{1} << '\n'; // 1996/Dec/Wed[1]
    std::cout << ymw - years{1} << '\n'; // 1996/Jan/Wed[1] 

    // year_month_weekday_last
    year_month_weekday_last ymwl{ year(1997) / January / Wednesday[last] };
    std::cout << ymwl - months{ 1 } << '\n'; // 1996/Dec/Wed[last]
    std::cout << ymwl - years{ 1 } << '\n'; // 1996/Jan/Wed[last]
    
    return 0;
}

05
Jan
Dec
21
2020
2021/Apr
2019/Jun
2020/May/last
1996/Dec/Wed[1]
1996/Jan/Wed[1]
1996/Dec/Wed[last]
1996/Jan/Wed[last]

Unary operator-

Negates a duration.

constexpr common_type_t<duration> operator-() const;

Return value

Returns a negated copy of *this

Example: unary operator-

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
   duration<int, std::milli> milliseconds(120);
   std::cout << -milliseconds << '\n';
   return 0;
}

-120ms

operator!=

Determines whether:

1) Two duration objects don't represent the same number of ticks.
2) Two time_point objects don't represent the same point in time.

1)
template <class Rep1, class Period1, class Rep2, class Period2>
constexpr bool operator!=(
    const duration<Rep1, Period1>& Left,
    const duration<Rep2, Period2>& Right);

2)
template <class Clock, class Duration1, class Duration2>
constexpr bool operator!=(
    const time_point<Clock, Duration1>& Left,
    const time_point<Clock, Duration2>& Right);

Parameters

Left
The left duration or time_point object.

Right
The right duration or time_point object.

Return value

1) Returns true if the number of ticks for the type common to Left and Right aren't equal. Otherwise, returns false.
2) Returns true if the two time_point objects don't represent the same point in time. Otherwise, returns false.

operator*

Multiplication operator for duration objects. After converting the durations being multiplied to their common type, returns a duration with a tick count equal to the multiplication of the converted tick counts.

1)
template <class Rep1, class Period1, class Rep2>
constexpr duration<typename common_type<Rep1, Rep2>::type, Period1>
   operator*(
      const duration<Rep1, Period1>& Dur,
      const Rep2& Mult);

2)
template <class Rep1, class Rep2, class Period2>
constexpr duration<typename common_type<Rep1, Rep2>::type, Period2>
   operator*(
       const Rep1& Mult,
       const duration<Rep2,
       Period2>& Dur);

Parameters

Dur
A duration object.

Mult
An integral value.

Return value

Returns a duration object whose interval length is Mult multiplied by the length of Dur.

1) Unless is_convertible<Rep2, common_type<Rep1, Rep2>>holds true, this function doesn't participate in overload resolution. For more information, see <type_traits>.

2) Unless is_convertible<Rep1, common_type<Rep1, Rep2>>holds true, this function doesn't participate in overload resolution. For more information, see <type_traits>.

operator<

1) After converting the durations being compared to their common type, determines if the number of ticks for Left is fewer than for Right.

2) Determines if the point in time since the epoch of the Lefttime_point is less than the time since the epoch of the time_point in Right.

1)
template <class Rep1, class Period1, class Rep2, class Period2>
constexpr bool operator<(
    const duration<Rep1, Period1>& Left,
    const duration<Rep2, Period2>& Right);

2)
template <class Clock, class Duration1, class Duration2>
constexpr bool operator<(
    const time_point<Clock, Duration1>& Left,
    const time_point<Clock, Duration2>& Right);

Parameters

Left
The left duration or time_point object.

Right
The right duration or time_point object.

Return value

1) Returns true if number of ticks for Left is less than the number of ticks for Right. Otherwise, the function returns false.

2) Returns true if Left precedes Right. Otherwise, returns false.

operator<=

1) After converting the durations being compared to their common type, determines if the number of ticks for Left is fewer or the same as Right.

2) Determines if the point in time since the epoch of the Lefttime_point is less than or equal to the time since the epoch of the time_point in Right.

1)
template <class Rep1, class Period1, class Rep2, class Period2>
constexpr bool operator<=(
    const duration<Rep1, Period1>& Left,
    const duration<Rep2, Period2>& Right);

2)
template <class Clock, class Duration1, class Duration2>
constexpr bool operator<=(
    const time_point<Clock, Duration1>& Left,
    const time_point<Clock, Duration2>& Right);

Parameters

Left
The left duration or time_point object.

Right
The right duration or time_point object.

Return value

1) Returns true if number of ticks for Left is less than or equal to the number of ticks for Right. Otherwise, the function returns false.

2) Returns true if Left precedes, or is equal to, Right. Otherwise, returns false.

operator==

Determines whether:

1) duration objects represent time intervals that have the same length.
2) time_point objects represent the same point in time.
3) day objects represent the same day.
4) month objects represent the same month.
5) month_day objects represent the same month and day.
6) month_day_last objects represent the same month.
7) month_weekday objects represent the same month and nth weekday.
8) month_weekday_last objects represent the same month and last weekday.
9) weekday objects represent the same weekday.
10) weekday_last objects represent the same last weekday of the month.
11) weekday_indexed represent the same weekday index.
12) year represent the same year.
13) year_month represent the same year and month.
14) year_month_day represent the same year, month, and day.
15) year_month_day_last represent the same last day of the year and month.
16) year_month_weekday represent the same weekday, year, and month.
17) year_month_weekday_last represent the same last weekday of the month, year, and month.
18) time_zone_link have the same name. The target name isn't considered.
19) zoned_time represent the same time and time zone.

// 1) duration<Rep, Period>
template <class Rep1, class Period1, class Rep2, class Period2>
constexpr bool operator==(
    const duration<Rep1, Period1>& Left,
    const duration<Rep2, Period2>& Right);

// 2) time_point
template <class Clock, class Duration1, class Duration2>
constexpr bool operator==(
    const time_point<Clock, Duration1>& Left,
    const time_point<Clock, Duration2>& Right);

// 3) day
constexpr bool operator==(const day& Left, const day& Right) noexcept; // C++20

// 4) month
constexpr bool operator==(const month& Left, const month& Right) noexcept; // C++20

// 5) month_day
constexpr bool operator==(const month_day& Left, const month_day& Right) noexcept; // C++20

// 6) month_day_last
constexpr bool operator==(const month_day_last& Left, const month_day_last& Right) noexcept; // C++20

// 7) month_weekday
constexpr bool operator==(const month_weekday& Left, const month_weekday& Right) noexcept; // C++20

// 8) month_weekday_last
constexpr bool operator==(const month_weekday_last& Left, const month_weekday_last& Right) noexcept; // C++20

// 9) weekday
constexpr bool operator==(const weekday& Left, const weekday& Right) noexcept; // C++20

// 10) weekday_last
constexpr bool operator==(const weekday_last& Left, const weekday_last& Right) noexcept; // C++20

// 11) weekday_indexed
constexpr bool operator==(const weekday_indexed& x, const weekday_indexed& y) noexcept; // C++20

// 12) year
constexpr bool operator==(const year& Left, const year& y ) noexcept; // C++20

// 13) year_month
constexpr bool operator==(const year_month& Left, const year_month& Right) noexcept; // C++20

// 14) year_month_day
constexpr bool operator==(const year_month_day& Left, const year_month_day& Right) noexcept; // C++20

// 15) year_month_day_last
constexpr bool operator==(const year_month_day_last& Left, const year_month_day_last& Right) noexcept; // C++20

// 16) year_month_weekday
constexpr bool operator==(const year_month_weekday& Left, const year_month_weekday& Right) noexcept; // C++20

// 17)  year_month_weekday_last
constexpr bool operator==(const year_month_weekday_last& Left, const year_month_weekday_last& Right) noexcept; // C++20

// 18) time_zone_link
bool operator==(const time_zone_link& Left, const time_zone_link& Right) noexcept; // C++20

// 19) zoned_time
template <class Duration1, class Duration2, class TimeZonePtr>
bool operator==(const zoned_time<Duration1, TimeZonePtr>& Left, const zoned_time<Duration2, TimeZonePtr>& Right); // C++20

Parameters

Left
The left object to compare, for example, Left == Right

Right
The right object to compare.

Return value

1) Returns true if the number of ticks for the type common to Left and Right are equal. Otherwise, returns false.
2) Returns true if Left and Right represent the same point in time. Otherwise, returns false.
3-17) Returns true if Left and Right have the same value. Otherwise, returns false.
18) Returns true if Left.name() == Right.name(). Otherwise, returns *false*.
19) Returns true if Left.get_time_zone() == _Right.get_time_zone() && Left.get_sys_time() == Right.get_sys_time();

operator>

1) After converting the durations being compared to their common type, determines if the number of ticks for Left is greater than for Right.

2) Determines if the point in time since the epoch of the Lefttime_point is greater than the time since the epoch of the time_point in Right.

1) 
template <class Rep1, class Period1, class Rep2, class Period2>
constexpr bool operator>(
    const duration<Rep1, Period1>& Left,
    const duration<Rep2, Period2>& Right);

2)
template <class Clock, class Duration1, class Duration2>
constexpr bool operator>(
    const time_point<Clock, Duration1>& Left,
    const time_point<Clock, Duration2>& Right);

Parameters

Left
The left duration or time_point object.

Right
The right duration or time_point object.

Return value

1) Returns true if number of ticks for Left is greater than the number of ticks for Right. Otherwise, the function returns false.

2) Returns true if Left comes after Right. Otherwise, returns false.

operator>=

1) After converting the durations being compared to their common type, determines if the number of ticks for Left is greater than or equal to Right.

2) Determines if the point in time since the epoch of the Lefttime_point is greater than or equal to the time since the epoch of the time_point in Right.

1)
template <class Rep1, class Period1, class Rep2, class Period2>
constexpr bool operator>=(
    const duration<Rep1, Period1>& Left,
    const duration<Rep2, Period2>& Right);

2)
template <class Clock, class Duration1, class Duration2>
constexpr bool operator>=(
    const time_point<Clock, Duration1>& Left,
    const time_point<Clock, Duration2>& Right);

Parameters

Left
The left duration or time_point object.

Right
The right duration or time_point object.

Return value

1) Returns true if number of ticks for Left is greater than or equal to the number of ticks for Right. Otherwise, the function returns false.

2) Returns true if Left comes after, or is equal to, Right. Otherwise, returns false.

operator<=>

The spaceship operator, with operator==, synthesizes operators for <, <=, >, >=, and != for the following types:

1)
constexpr bool operator<=>(const day& Left, const day& Right) noexcept; // C++20

constexpr std::strong_ordering operator<=>(const month& Left, const month& Right) noexcept; // C++20

constexpr strong_ordering operator<=>(const month_day& Left, const month_day& Right) noexcept; // C++20

constexpr std::strong_ordering operator<=>(const year& Left, const year& Right ) noexcept; // C++20

constexpr strong_ordering operator<=>(const year_month& Left, const year_month& Right) noexcept; // C++20

template<class Clock, class Duration1, three_­way_­comparable_­with<Duration1> Duration2>
    constexpr auto operator<=>(const time_point<Clock, Duration1>& Left, const time_point<Clock, Duration2>& Right); // C++20

template<class Rep1, class Period1, class Rep2, class Period2>
  requires three_­way_­comparable<typename CT::rep>
    constexpr auto operator<=>(const duration<Rep1, Period1>& Left, const duration<Rep2, Period2>& Right);

2)
constexpr strong_ordering operator<=>(const month_day_last& Left, const month_day_last& Right) noexcept;

3)
constexpr strong_ordering operator<=>(const year_month_day_last& Left, const year_month_day_last& Right) noexcept;

4)
strong_ordering operator<=>(const time_zone_link& Left, const time_zone_link& Right) noexcept;

Parameters

Left, Right
The day, duration, month, month_day, month_day_last, time_point, time_zone_link, year, year_month, year_month_day, year_month_day_last to compare.

Return value

1)
0 if Left == Right
< 0 if Left < Right
> 0 if Left > Right

2)
Equivalent to: Left.month() <=> Right.month()

3)
Equivalent to:

if (auto c = Left.year() <=> Right.year(); c != 0) return c;
return Left.month_day_last() <=> Right.month_day_last();

4)
Equivalent to:

Left.name() <=> Right.name()

Example: operator<=>

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono; // for day and 'd' literals

int main()
{
    day d1{3};
    day d2{2};

    if ((d1 <=> d2) == 0)
    {
        std::cout << "equal\n";
    }
    else if ((d1 <=> d2) < 0)
    {
        std::cout << "d1 < d2\n";
    }
    else if ((d1 <=> d2) > 0)
    {
        std::cout << "d1 > d2\n";
    }

    std::cout << std::boolalpha << (1d <= 1d) << ' ' << (1d != 2d) << ' ' << (2d > 3d);

    return 0;
}

d1 < d2
true true false

operator<<

Output the following types to a stream:

// 1) day
template <class CharT, class Traits>
std::basic_ostream<CharT, Traits>&
operator<<(std::basic_ostream<CharT, Traits>& os, const day& d); // C++20

// 2) hh_mm_ss
template<class CharT, class traits, class Duration>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const hh_mm_ss<Duration>& hms); // C++20

// 3) month
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const month& m); // C++20

// 4) month_day
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const month_day& md); // C++20

// 5) month_day_last
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const month_day_last& mdl); // C++20

// 6) month_weekday
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const month_weekday& mwd); // C++20

// 7) month_weekday_last
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const month_weekday_last& mwdl); // C++20

// 8) weekday
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const weekday& wd); // C++20

// 9) weekday_indexed
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const weekday_indexed& wdi); // C++20

// 10) weekday_last
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const weekday_last& wdl); // C++20

// 11) year
template <class CharT, class Traits>
std::basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const year& y); // C++20

// 12) year_month
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const year_month& ym); // C++20

// 13) year_month_day
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const year_month_day& ymd); // C++20

// 14) year_month_day_last
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const year_month_day_last& ymdl); // C++20

// 15) year_month_weekday
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const year_month_weekday& ymwd); // C++20

// 16) year_month_weekday_last
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const year_month_weekday_last& ymwdl); // C++20

// 17) tai_time
template<class CharT, class Traits, class Duration>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const tai_time<Duration>& t); // C++20

// 18) utc_time
template<class CharT, class Traits, class Duration>
basic_ostream<CharT, traits>&
operator<<(basic_ostream<CharT, Traits>& os, const utc_time<Duration>& t); // C++20

// 19) gps_time
template<class CharT, class Traits, class Duration>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const gps_time<Duration>& t); // C++20

// 20) local_time
template<class CharT, class Traits, class Duration>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const local_time<Duration>& t); // C++20

// 21) sys_info
template<class CharT, class Traits>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const sys_info& si);

// 22) local_info
template<class CharT, class Traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<CharT, Traits>& os, const local_info& li);

// 23) zoned_time
template<class CharT, class Traits, class Duration, class TimeZonePtr>
basic_ostream<CharT, Traits>&
operator<<(basic_ostream<CharT, Traits>& os, const zoned_time<Duration, TimeZonePtr>& zt);

Parameters

CharT
The data type of a single character to be read from the stream and stored in the string. The C++ Standard Library provides specializations of this class template, with the type definitions string for elements of type char, wstring, for wchar_t, u16string for char16_t, and u32string for char32_t.

Traits
Describes CharT attributes for the basic_string and basic_istream specialization.

os
The output stream to emit the day value into.

d
The day to output.

hms
The hh_mm_ss to output.

li
The local_info to output.

m
The month to output.

md
The month_day to output.

mdl
The month_day_last to output.

mwd
The month_weekday to output.

mwdl
The month_weekday_last to output.

si
The sys_info to output.

t
The local_time, gps_time, tai_time, or utc_time to output.

TimeZonePtr
A pointer to the time_zone stored in the zoned_time.

wd
The weekday to output.

wdi
The weekday_indexed to output.

wdl
The weekday_last to output.

y
The year to output.

ym
The year_month to output.

ymd
The year_month_day to output.

ymdl
The year_month_day_last to output.

ymwd
The year_month_weekday to output.

ymwdl
The year_month_weekday_last to output.

zt
The zoned_time to output.

Return value

The output stream you passed in, os

Remarks

1) The day value is output as a decimal number, with a leading zero if the result would be a single digit. If !d.ok(), then " isn't a valid day" is appended to the output.

2) The hh_mm_ss value is output as hours:minutes:seconds:thousandths of seconds. For example, "00:00:05.721"

3) The abbreviated month name, using the locale associated with os, is output. For example, Jan. If !m.ok(), then " is not a valid month" is appended to the output.

4) The abbreviated month name, using the locale associated with os, followed by the date, with a leading zero if the result would be a single digit, is output. For example, Jan/05. If !md.ok(), then " is not a valid month" may be appended to the output of the month, and "is not a valid day" may be appended to the output of the day. For example, 204 is not a valid month/204 is not a valid day.

5) The abbreviated month name, using the locale associated with os, followed by /last. For example, Jan/last.

6) The abbreviated weekday name, using the locale associated with os, followed by the nth weekday in the month it represents in brackets. For example, Mon[1].

7) The abbreviated weekday name, using the locale associated with os, followed by the last weekday in the month it represents in brackets. For example, Jan/Mon[last].

8) The abbreviated weekday name, using the locale associated with os, is output. If !wd.ok(), then " is not a valid weekday" is appended to the output.

9) The abbreviated weekday name, using the locale associated with os, is output, followed by the weekday of the month in brackets. For example, Mon[3]. If !wd.ok(), then " is not a valid weekday" may be appended to the day of the week output, and "is not a valid index" may be appended to the weekday index output.

10) The last weekday of a month, using the locale associated with os, is output, followed by [last], followed by the date. For example, Tue[last] 2019-10-29. If !wd.ok(), then " is not a valid weekday" may be appended to the day of the week output, and "is not a valid index" may be appended to the weekday index output.

11) The year is left-padded with 0 (zero) to four digits if the result would be less than that. If !y.ok(), then " is not a valid year" is appended to the output.

12) The year_month is output in the form yyy-mm-dd. If ym.ok returns false, then " is not a valid date" is appended.

13) The year_month_day is output in the form yyyy-mm-dd. If ymd.ok returns false, then " is not a valid date" is appended.

14) The year_month_day_last is output in the form yyyy/month/last. For example, 2020/May/last.

15) The year_month_weekday is output in the form yyyy/month/weekday[index]. For example, 1996/Jan/Wed[1]

16) The year_month_weekday_last is output in the form yyyy/month/weekday[last]. For example, 1996/Jan/Wed[last]

17) The tai_time is output in the form yyyy-mm-dd hh:mm:ss.sssssss. For example, 2021-08-13 23:23:08.4358666

18) The utc_time is output in the form yyyy-mm-dd hh:mm:ss.sssssss. For example, 2021-08-13 23:23:08.4358666

19) The gps_time is output in the form yyyy-mm-dd hh:mm:ss.sssssss. For example, 2021-08-13 23:23:08.4358666

20) The local_time is output as the number of seconds since the clock's epoch. It's output as though by os << std::chrono::sys_time<Duration>(some_local_time.time_since_epoch());. For example, if some_local_time is August 18, 2021 3:13pm, the output is 1597792380.

21) In Microsoft's implementation, a sys_info is output as its begin, end, offset, save, and abbrev fields. For example: begin: 2021-03-14 10:00:00, end: 2021-11-07 09:00:00, offset: -25200s, save: 60min, abbrev: PDT

22) In Microsoft's implementation, a local_info is output as yyyy-mm-dd hh:mm::ss.ssssss. For example, 2021-09-17 13:55:59.6590120

23) The local time in the zoned_time (obtained as zt.get_local_time()) is output using the format yyyy-mm-dd hh:mm:ss timezone. For example, 2021-09-15 10:45:00 GMT-6

Example: operator<<

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
    std::cout << utc_clock::now() << '\n';

    year_month ym{ 2021y / April };
    std::cout << ym;
    return 0;
}

2021-08-16 20:47:05.6299822
2021/Apr

operator modulo

Operator for modulo operations on duration.

1)
template <class Rep1, class Period1, class Rep2>
constexpr duration<Rep1, Period1, Rep2>::type
   operator%(
      const duration<Rep1, Period1>& Dur,
      const Rep2& Div);

2)
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>& Left,
     const duration<Rep2, Period2>& Right);

Parameters

Dur
A duration object.

Div
An integral value.

Left
The dividend. The modulo is the remainder after dividing the dividend by the divisor.

Right
The right duration object, the divisor.

Return value

1) Returns a duration object whose interval length is Dur modulo Div.

2) Returns a value that represents Left modulo Right.

operator/ for duration

Division operator for duration objects.

1)
template <class Rep1, class Period1, class Rep2>
constexpr duration<typename common_type<Rep1, Rep2>::type, Period1>
   operator/(
     const duration<Rep1, Period1>& Dur,
     const Rep2& Div);

2)
template <class Rep1, class Period1, class Rep2, class Period2>
constexpr typename common_type<Rep1, Rep2>::type
   operator/(
     const duration<Rep1, Period1>& Left,
     const duration<Rep2, Period2>& Right);

Parameters

Dur
A duration object.

Div
An integral value.

Left\w The left duration object.

Right
The right duration object.

Return value

1) A duration object whose interval length is the length of Dur divided by the value Div.

2) The ratio of the interval lengths of Left and Right.

Unless is_convertible<Rep2, common_type<Rep1, Rep2>>holds true, and Rep2 isn't an instantiation of duration, the first operator doesn't participate in overload resolution. For more information, see <type_traits>.

operator/ for calendar dates

Provides syntax to create calendar dates in the following forms:

month/day/year
day/month/year
year/month/day

You can replace day with:

last
weekday[n] for the nth day of the month
weekday[last] for the last weekday of the month.

Partial dates can be formed as follows:

year_month ym = 2015y/April;
month_day md1 = April/4;
month_day md2 = 4d/April;

Integers can be used as long as the interpretation isn't ambiguous.

/////////  returns year_month

// 1
constexpr year_month
operator/(const year& y, const month& m) noexcept; // C++20

// 2
constexpr year_month
operator/(const year& y, int m) noexcept; // C++20
 
/////////  returns month_day

// 3
constexpr month_day
operator/(const month& m, const day& d) noexcept; // C++20

// 4
constexpr month_day
operator/(const month& m, int d) noexcept; // C++20

// 5
constexpr month_day
operator/(int m, const day& d) noexcept; // C++20

// 6
constexpr month_day
operator/(const day& d, const month& m) noexcept; // C++20

// 7
constexpr month_day
operator/(const day& d, int m) noexcept; // C++20

/////////  returns month_day_last

// 8
constexpr month_day_last
operator/(const month& m, last_spec) noexcept; // C++20

// 9
constexpr month_day_last
operator/(int m, last_spec) noexcept; // C++20

// 10
constexpr month_day_last
operator/(last_spec, const month& m) noexcept; // C++20

// 11
constexpr month_day_last
operator/(last_spec, int m) noexcept; // C++20

/////////  returns month_weekday

// 12
constexpr month_weekday
operator/(const month& m, const weekday_indexed& wdi) noexcept; // C++20

// 13
constexpr month_weekday
operator/(int m, const weekday_indexed& wdi) noexcept; // C++20

// 14
constexpr month_weekday
operator/(const weekday_indexed& wdi, const month& m) noexcept; // C++20

// 15
constexpr month_weekday
operator/(const weekday_indexed& wdi, int m) noexcept; // C++20

/////////  returns month_weekday_last

// 16
constexpr month_weekday_last
operator/(const month& m, const weekday_last& wdl) noexcept; // C++20

// 17
constexpr month_weekday_last
operator/(int m, const weekday_last& wdl) noexcept; // C++20

// 18
constexpr month_weekday_last
operator/(const weekday_last& wdl, const month& m) noexcept; // C++20

// 19
constexpr month_weekday_last
operator/(const weekday_last& wdl, int m) noexcept; // C++20

/////////  returns year_month_day

// 20
constexpr year_month_day
operator/(const year_month& ym, const day& d) noexcept; // C++20

// 21
constexpr year_month_day
operator/(const year_month& ym, int d) noexcept; // C++20

// 22
constexpr year_month_day
operator/(const year& y, const month_day& md) noexcept; // C++20

// 23
constexpr year_month_day
operator/(int y, const month_day& md) noexcept; // C++20

// 24
constexpr year_month_day
operator/(const month_day& md, const year& y) noexcept; // C++20

// 25
constexpr year_month_day
operator/(const month_day& md, int y) noexcept; // C++20

/////////  returns year_month_day_last

// 26
constexpr year_month_day_last
operator/(const year_month& ym, last_spec) noexcept; // C++20

// 27
constexpr year_month_day_last
operator/(const year& y, const month_day_last& mdl) noexcept; // C++20

// 28
constexpr year_month_day_last
operator/(int y, const month_day_last& mdl) noexcept; // C++20

// 29
constexpr year_month_day_last
operator/(const month_day_last& mdl, const year& y) noexcept; // C++20

// 30
constexpr year_month_day_last
operator/(const month_day_last& mdl, int y) noexcept; // C++20

/////////  returns year_month_weekday

// 31
constexpr year_month_weekday
operator/(const year_month& ym, const weekday_indexed& wdi) noexcept; // C++20

// 32
constexpr year_month_weekday
operator/(const year& y, const month_weekday& mwd) noexcept; // C++20

// 33
constexpr year_month_weekday
operator/(int y, const month_weekday& mwd) noexcept; // C++20

// 34
constexpr year_month_weekday
operator/(const month_weekday& mwd, const year& y) noexcept; // C++20

// 35
constexpr year_month_weekday
operator/(const month_weekday& mwd, int y) noexcept; // C++20

/////////  returns year_month_weekday_last

// 36
constexpr year_month_weekday_last
operator/(const year_month& ym, const weekday_last& wdl) noexcept; // C++20

// 37
constexpr year_month_weekday_last
operator/(const year& y, const month_weekday_last& mwdl) noexcept; // C++20

// 38
constexpr year_month_weekday_last
operator/(int y, const month_weekday_last& mwdl) noexcept; // C++20

// 39
constexpr year_month_weekday_last
operator/(const month_weekday_last& mwdl, const year& y) noexcept; // C++20

// 40
constexpr year_month_weekday_last
operator/(const month_weekday_last& mwdl, int y) noexcept; // C++20

Parameters

d
The day. Provided either as an integer in the range [1,31], or as a day.

lastspec
An empty tag type that indicates the last item in s sequence. For example, 2021y/May/last is the last day of May 2021.

m
The month. Provided either as an integer in the range [1,12], or as a month.

md
The month and day.

mdl
The last day of the specified month.

mwd
The n-th weekday of the specified month.

mwdl
The last weekday of the specified month.

wdi
A weekday index (weekday_indexed). For example, weekday_indexed(Monday, 1) is the first Monday of a month.

wdl
The last weekday of a month. For example, Monday[last] is the last Monday of a month.

y
The year. Provided either as an integer, or as a year.

ym
The year and month.

Return value

1) year_month(y, m)
2) year_month(y, month(m))
3) month_day(m, d)
4) month_day(m, day(d))
5) month_day(month(m), d)
6) month_day(m, d)
7) month_day(month(m), d)
8) month_day_last(m)
9) month_day_last(month(m))
10) month_day_last(m)
11) month_day_last(month(m))
12) month_weekday(m, wdi)
13) month_weekday(month(m), wdi)
14) month_weekday(m, wdi)
15) month_weekday(month(m), wdi)
16) month_weekday_last(m, wdl)
17) month_weekday_last(month(m), wdl)
18) month_weekday_last(m, wdl)
19) month_weekday_last(month(m), wdl)
20) year_month_day(ym.year(), ym.month(), d)
21) year_month_day(ym.year(), ym.month(), day(d))
22) year_month_day(y, md.month(), md.day())
23) year_month_day(year(y), md.month(), md.day())
24) year_month_day(y, md.month(), md.day())
25) year_month_day(year(y), md.month(), md.day())
26) year_month_day_last(ym.year(), month_day_last(ym.month()))
27) year_month_day_last(y, mdl)
28) year_month_day_last(year(y), mdl)
29) year_month_day_last(y, mdl)
30) year_month_day_last(year(y), mdl)
31) year_month_weekday(ym.year(), ym.month(), wdi)
32) year_month_weekday(y, mwd.month(), mwd.weekday_indexed())
33) year_month_weekday(year(y), mwd.month(), mwd.weekday_indexed())
34) year_month_weekday(y, mwd.month(), mwd.weekday_indexed())
35) year_month_weekday(year(y), mwd.month(), mwd.weekday_indexed())
36) year_month_weekday_last(ym.year(), ym.month(), wdl)
37) year_month_weekday_last(y, mwdl.month(), mwdl.weekday_last())
38) year_month_weekday_last(year(y), mwdl.month(), mwdl.weekday_last())
39) year_month_weekday_last(y, mwdl.month(), mwdl.weekday_last())
40) year_month_weekday_last(year(y), mwdl.month(), mwdl.weekday_last())

Example: operator/ for calendar dates

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
    month m{ July }; // Jul
    month_day md{ April / 4 }; // Apr/04
    month_day md2{ 4d / April }; // Apr/04
    month_day_last mdl{ January / last }; // Jan/last
    month_weekday mw{ 11 / Monday[1] }; // Nov/Mon[1]
    month_weekday_last mwl{ January / Monday[last] }; // Jan/Mon[last]
    weekday wd{ Monday }; // Mon
    weekday_indexed wdi{ Monday, 1 }; // Mon[1]
    year_month ym{ 2021y / April }; // 2021/Apr
    year_month_day ymd{ January / 1d / 2021y }; // 2021-01-01
    year_month_day ymd2{ 2021y / 5 / 7 }; // 2021-05-07
    year_month_day_last ymdl{ April / last / 1975 }; // 1975/Apr/last
    year_month_weekday ymw{ 1997y / January / Wednesday[1] }; // 1997/Jan/Wed[1]
    year_month_weekday_last ymwl{ 1997y / January / Wednesday[last] }; // 1997/Jan/Wed[last]
    int yearValue{ 2021 / 4 / 4 }; // 126

    std::cout << m << '\n' << md << '\n' << md2 << '\n' << mdl << '\n' << mw
        << '\n' << mwl << '\n' << wd << '\n' << wdi << '\n'
        << ym << '\n' << ymd << '\n' << ymd2 << '\n' << ymdl
        << '\n' << ymw << '\n' << ymwl << '\n' << yearValue;

    return 0;
}

Jul
Apr/04
Apr/04
Jan/last
Nov/Mon[1]
Jan/Mon[last]
Mon
Mon[1]
2021/Apr
2021-01-01
2021-05-07
1975/Apr/last
1997/Jan/Wed[1]
1997/Jan/Wed[last]
126