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

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chrono I/O
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C-style date and time
std::chrono::year_month_weekday
constexpr std::chrono::year_month_weekday &
    operator+ = ( const std::chrono::years & dy ) const noexcept ;
(1) (since C++20)
constexpr std::chrono::year_month_weekday &
    operator+ = ( const std::chrono::months & dm ) const noexcept ;
(2) (since C++20)
constexpr std::chrono::year_month_weekday &
    operator- = ( const std::chrono::years & dy ) const noexcept ;
(3) (since C++20)
constexpr std::chrono::year_month_weekday &
    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)

Example

Run this code
#include <cassert>
#include <chrono>
#include <iostream>
 
int main()
{
    auto ymwi{1/std::chrono::Wednesday[2]/2021};
    std::cout << ymwi << '\n';
 
    ymwi += std::chrono::years(5);
    std::cout << ymwi << '\n';
    assert(static_cast<std::chrono::year_month_day>(ymwi) ==
                       std::chrono::year(2026)/1/14);
 
    ymwi -= std::chrono::months(1);
    std::cout << ymwi << '\n';
    assert(static_cast<std::chrono::year_month_day>(ymwi) == 
                       std::chrono::day(10)/12/2025);
}

Output: 

2021/Jan/Wed[2]
2026/Jan/Wed[2]
2025/Dec/Wed[2]

See also

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