std::chrono::operator+, std::chrono::operator- (std::chrono::year_month_weekday)

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Date and time library

Time point time_point (C++11) clock_time_conversion (C++20)   clock_cast (C++20) Duration duration (C++11) Clocks system_clock (C++11) steady_clock (C++11) is_clock (C++20) utc_clock (C++20) tai_clock (C++20) high_resolution_clock (C++11) gps_clock (C++20) file_clock (C++20) local_t (C++20) Time of day is_amis_pm (C++20)(C++20) make12make24 (C++20)(C++20) hh_mm_ss (C++20)

Calendar day (C++20) month (C++20) year (C++20) weekday (C++20) operator/ (C++20) year_month_day (C++20) year_month_day_last (C++20) year_month_weekday (C++20) year_month_weekday_last (C++20)   weekday_indexed (C++20) weekday_last (C++20) month_day (C++20) month_day_last (C++20) month_weekday (C++20) month_weekday_last (C++20) year_month (C++20) last_speclast (C++20)(C++20) chrono I/O parse (C++20)

Time zone tzdb (C++20) tzdb_list (C++20) get_tzdbget_tzdb_listreload_tzdbremote_version (C++20)(C++20)(C++20)(C++20) sys_info (C++20) local_info (C++20) nonexistent_local_time (C++20) ambiguous_local_time (C++20) locate_zone (C++20) current_zone (C++20) time_zone (C++20) choose (C++20) zoned_traits (C++20) zoned_time (C++20) time_zone_link (C++20) leap_second (C++20) leap_second_info (C++20) get_leap_second_info (C++20) C-style date and time

 

std::chrono::year_month_weekday

Member functions

year_month_weekday::year_month_weekday

year_month_weekday::operator+=year_month_weekday::operator-=

year_month_weekday::yearyear_month_weekday::monthyear_month_weekday::weekdayyear_month_weekday::indexyear_month_weekday::weekday_indexed

year_month_weekday::operator sys_daysyear_month_weekday::operator local_days

year_month_weekday::ok

Nonmember functions

operator==

operator+operator-

operator<<

Helper classes

formatter<std::chrono::year_month_weekday>

hash<std::chrono::year_month_weekday> (C++26)

 

constexpr std::chrono::year_month_weekday operator+( const std::chrono::year_month_weekday& ymwd, const std::chrono::months& dm ) noexcept;	(1)	(since C++20)
constexpr std::chrono::year_month_weekday operator+( const std::chrono::months& dm, const std::chrono::year_month_weekday& ymwd ) noexcept;	(2)	(since C++20)
constexpr std::chrono::year_month_weekday operator+( const std::chrono::year_month_weekday& ymwd, const std::chrono::years& dy ) noexcept;	(3)	(since C++20)
constexpr std::chrono::year_month_weekday operator+( const std::chrono::years& dy, const std::chrono::year_month_weekday& ymwd ) noexcept;	(4)	(since C++20)
constexpr std::chrono::year_month_weekday operator-( const std::chrono::year_month_weekday& ymwd, const std::chrono::months& dm ) noexcept;	(5)	(since C++20)
constexpr std::chrono::year_month_weekday operator-( const std::chrono::year_month_weekday& ymwd, const std::chrono::years& dy ) noexcept;	(6)	(since C++20)

1,2) Adds dm.count() months to the date represented by ymwd. The result has the same year() and month() as std::chrono::year_month(ymwd.year(), ymwd.month()) + dm and the same weekday() and index() as ymwd.

3,4) Adds dy.count() years to the date represented by ymwd. The result is equivalent to std::chrono::year_month_weekday(ymwd.year() + dy, ymwd.month(), ymwd.weekday_indexed()).

5) Subtracts dm.count() months from the date represented by ymwd. Equivalent to ymwd + -dm.

6) Subtracts dy.count() years from the date represented by ymwd. Equivalent to ymwd + -dy.

For durations that are convertible to both std::chrono::years and std::chrono::months, the years overloads (3,4,6) are preferred if the call would otherwise be ambiguous.

Notes

Even if ymwd.ok() is true, the resulting year_month_weekday may not represent a valid date if ymwd.index() is 5.

Example

Run this code

#include <cassert>
#include <chrono>
#include <iostream>

int main()
{
    auto ymwdi{1/std::chrono::Wednesday[1]/2021};
    std::cout << ymwdi << '\n';

    ymwdi = std::chrono::years(5) + ymwdi;
    // First Wednesday in January, 2026
    std::cout << ymwdi << '\n';
    assert(static_cast<std::chrono::year_month_day>(ymwdi) ==
           std::chrono::January/7/2026);

    ymwdi = ymwdi - std::chrono::months(6);
    // First Wednesday in July, 2025
    std::cout << ymwdi << '\n';
    assert(static_cast<std::chrono::year_month_day>(ymwdi) ==
           std::chrono::July/2/2025);
}

Output:

2021/Jan/Wed[1]
2026/Jan/Wed[1]
2025/Jul/Wed[1]