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std::chrono::year_month_weekday_last:: operator+=, std::chrono::year_month_weekday_last:: operator-=

From cppreference.net

C++
Date and time library
std::chrono::year_month_weekday_last
constexpr std:: chrono :: year_month_weekday_last &
operator + = ( const std:: chrono :: years & dy ) const noexcept ;
(1) (since C++20)
constexpr std:: chrono :: year_month_weekday_last &
operator + = ( const std:: chrono :: months & dm ) const noexcept ;
(2) (since C++20)
constexpr std:: chrono :: year_month_weekday_last &
operator - = ( const std:: chrono :: years & dy ) const noexcept ;
(3) (since C++20)
constexpr std:: chrono :: year_month_weekday_last &
operator - = ( const std:: chrono :: months & dm ) const noexcept ;
(4) (since C++20)

Modifies the time point * this represents by the duration dy or dm .

1) Equivalent to * this = * this + dy ; .
2) Equivalent to * this = * this + dm ; .
3) Equivalent to * this = * this - dy ; .
4) Equivalent to * this = * this - dm ; .

For durations that are convertible to both std::chrono::years and std::chrono::months , the years overloads (1,3) are preferred if the call would otherwise be ambiguous.

Example

Run this code 
#include <chrono>
#include <iostream>
using namespace std::chrono;
int main()
{
    auto ymwdl{August/Friday[last]/2022};
    std::cout << year_month_day{ymwdl} << '\n';
    ymwdl += months(2);
    std::cout << year_month_day{ymwdl} << '\n';
    ymwdl -= years(1); 
    std::cout << year_month_day{ymwdl} << '\n';
}

Output: 

2022-08-26
2022-10-28
2021-10-29

See also

(C++20)
adds or subtracts a year_month_weekday_last and some number of years or months
(function)