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

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Defined in header <chrono>
constexpr std::chrono::year_month_day_last

    operator+( const std::chrono::year_month_day_last& ymdl,

               const std::chrono::months& dm ) noexcept;
(since C++20)
constexpr std::chrono::year_month_day_last

    operator+( const std::chrono::months& dm,

               const std::chrono::year_month_day_last& ymdl ) noexcept;
(since C++20)
constexpr std::chrono::year_month_day_last

    operator+( const std::chrono::year_month_day_last& ymdl,

               const std::chrono::years& dy ) noexcept;
(since C++20)
constexpr std::chrono::year_month_day_last

    operator+( const std::chrono::years& dy,

               const std::chrono::year_month_day_last& ymdl ) noexcept;
(since C++20)
constexpr std::chrono::year_month_day_last

    operator-( const std::chrono::year_month_day_last& ymdl,

               const std::chrono::months& dm ) noexcept;
(since C++20)
constexpr std::chrono::year_month_day_last

    operator-( const std::chrono::year_month_day_last& ymdl,

               const std::chrono::years& dy ) noexcept;
(since C++20)
1,2) Adds dm.count() months to the date represented by ymdl. The result has the same year() and month() as std::chrono::year_month(ymdl.year(), ymdl.month()) + dm.
3,4) Adds dy.count() years to the date represented by ymdl. The result is equivalent to std::chrono::year_month_day_last(ymdl.year() + dy, ymdl.month_day_last()).
5) Subtracts dm.count() months from the date represented by ymdl. Equivalent to ymdl + -dm.
6) Subtracts dy.count() years from the date represented by ymdl. Equivalent to ymdl + -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.

[edit] Example

#include <cassert>
#include <chrono>
#include <iostream>
 
int main()
{
    auto ymdl{11/std::chrono::last/2020};
    std::cout << ymdl << '\n';
 
    ymdl = std::chrono::years(10) + ymdl;
    std::cout << ymdl << '\n';
    assert(ymdl == std::chrono::day(30)/
                   std::chrono::November/
                   std::chrono::year(2030));
 
    ymdl = ymdl - std::chrono::months(6);
    std::cout << ymdl << '\n';
    assert(ymdl == std::chrono::day(31)/
                   std::chrono::May/
                   std::chrono::year(2030));
}

Output:

2020/Nov/last
2030/Nov/last
2030/May/last