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

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C-style date and time
std::chrono::year_month_weekday_last
(since C++20)
(since C++20)
(since C++20)
(since C++20)
(since C++20)
(since C++20)
1,2) Adds dm. count ( ) months to the date represented by ymwdl . The result has the same year() and month() as std:: chrono :: year_month ( ymwdl. year ( ) , ymwdl. month ( ) ) + dm and the same weekday() as ymwdl .
3,4) Adds dy. count ( ) years to the date represented by ymwdl . The result is equivalent to std:: chrono :: year_month_weekday_last ( ymwdl. year ( ) + dy, ymwdl. month ( ) , ymwd. weekday_last ( ) ) .
5) Subtracts dm. count ( ) months from the date represented by ymwdl . Equivalent to ymwdl + - dm .
6) Subtracts dy. count ( ) years from the date represented by ymwdl . Equivalent to ymwdl + - 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.

Example

Run this code 
#include <cassert>
#include <chrono>
using namespace std::chrono;
 
int main()
{
    constexpr auto ymwdl1{Tuesday[last]/11/2021};
    auto ymwdl2 = ymwdl1;
    ymwdl2 = std::chrono::months(12) + ymwdl2;
    ymwdl2 = ymwdl2 - std::chrono::years(1);
    assert(ymwdl1 == ymwdl2);
}
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