NAME¶

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

Synopsis¶

Defined in header <chrono>
constexpr std::chrono::year_month_day operator+( const
std::chrono::year_month_day& ymd,

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

) noexcept;
constexpr std::chrono::year_month_day operator+( const
std::chrono::months& dm,

const (since C++20)
std::chrono::year_month_day& ymd

) noexcept;
constexpr std::chrono::year_month_day operator+( const
std::chrono::year_month_day& ymd,

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

) noexcept;
constexpr std::chrono::year_month_day operator+( const
std::chrono::years& dy,

const (since C++20)
std::chrono::year_month_day& ymd

) noexcept;
constexpr std::chrono::year_month_day operator-( const
std::chrono::year_month_day& ymd,

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

) noexcept;
constexpr std::chrono::year_month_day operator-( const
std::chrono::year_month_day& ymd,

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

) noexcept;

1,2) Adds dm.count() months to the date represented by ymd. The result has the same
day() as ymd and the same year() and month() as std::chrono::year_month(ymd.year(),
ymd.month()) + dm.
3,4) Adds dy.count() years to the date represented by ymd. The result is equivalent
to std::chrono::year_month_day(ymd.year() + dy, ymd.month(), ymd.day().
5) Subtracts dm.count() months from the date represented by ymd. Equivalent to ymd +
-dm.
6) Subtracts dy.count() years from the date represented by ymd. Equivalent to ymd +
-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 ymd.ok() is true, the resulting year_month_day may not represent a valid
date if ymd.day() is 29, 30, or 31.

Example¶

// Run this code

#include <chrono>
#include <iostream>

int main()
{
std::cout << std::boolalpha;

auto ymd{std::chrono::day(1)/std::chrono::July/2021};

ymd = ymd + std::chrono::months(4);
std::cout << (ymd.month() == std::chrono::November) << ' '
<< (ymd.year() == std::chrono::year(2021)) << ' ';

ymd = ymd - std::chrono::years(10);
std::cout << (ymd.month() == std::chrono::month(11)) << ' '
<< (ymd.year() == std::chrono::year(2011)) << '\n';
}

Output:¶

true true true true