NAME¶

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

Synopsis¶

constexpr std::chrono::year_month_weekday

operator+( const std::chrono::year_month_weekday& ymwd, (1) (since C++20)

const std::chrono::months& dm ) noexcept;
constexpr std::chrono::year_month_weekday

operator+( const std::chrono::months& dm, (2) (since C++20)

const std::chrono::year_month_weekday& ymwd )
noexcept;
constexpr std::chrono::year_month_weekday

operator+( const std::chrono::year_month_weekday& ymwd, (3) (since C++20)

const std::chrono::years& dy ) noexcept;
constexpr std::chrono::year_month_weekday

operator+( const std::chrono::years& dy, (4) (since C++20)

const std::chrono::year_month_weekday& ymwd )
noexcept;
constexpr std::chrono::year_month_weekday

operator-( const std::chrono::year_month_weekday& ymwd, (5) (since C++20)

const std::chrono::months& dm ) noexcept;
constexpr std::chrono::year_month_weekday

operator-( const std::chrono::year_month_weekday& ymwd, (6) (since C++20)

const std::chrono::years& dy ) noexcept;

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]