# std::chrono::operator+, std::chrono::operator- (std::chrono::year_month_weekday)

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< cpp‎ | chrono‎ | year month weekday

constexpr std::chrono::year_month_weekday operator+( const std::chrono::year_month_weekday& ymwd, const std::chrono::months& dm ) noexcept; | (1) | (since C++20)
constexpr std::chrono::year_month_weekday operator+( const std::chrono::months& dm, const std::chrono::year_month_weekday& ymwd ) noexcept; | (2) | (since C++20)
constexpr std::chrono::year_month_weekday operator+( const std::chrono::year_month_weekday& ymwd, const std::chrono::years& dy ) noexcept; | (3) | (since C++20)
constexpr std::chrono::year_month_weekday operator+( const std::chrono::years& dy, const std::chrono::year_month_weekday& ymwd ) noexcept; | (4) | (since C++20)
constexpr std::chrono::year_month_weekday operator-( const std::chrono::year_month_weekday& ymwd, const std::chrono::months& dm ) noexcept; | (5) | (since C++20)
constexpr std::chrono::year_month_weekday operator-( const std::chrono::year_month_weekday& ymwd, const std::chrono::years& dy ) noexcept; | (6) | (since C++20)

1-2) Adds dm.count() months to the date represented by `ymwd`. The result has the same `year()` and `month()` as std::chrono::year_month(ymwd.year(), ymwd.month()) + dm and the same `weekday()` and `index()` as `ymwd`.
3-4) Adds dy.count() years to the date represented by `ymwd`. The result is equivalent to std::chrono::year_month_weekday(ymwd.year() + dy, ymwd.month(), ymwd.weekday_indexed()).
5) Subtracts dm.count() months from the date represented by `ymwd`. Equivalent to ymwd + -dm.
6) Subtracts dy.count() years from the date represented by `ymwd`. Equivalent to ymwd + -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 ymwd.ok() is true, the resulting `year_month_weekday` may not represent a valid date if ymwd.index() is 5.

### Example

Run this code

    #include <iostream>
    #include <chrono>

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

        auto ymwdi {1/std::chrono::Wednesday[1]/2021};
        ymwdi = std::chrono::years(5) + ymwdi;
        // First Wednesday in January, 2026
        std::cout << (static_cast<std::chrono::year_month_day>(ymwdi) ==
                      std::chrono::January/7/2026) << ' ';
        ymwdi = ymwdi - std::chrono::months(6);
        // First Wednesday in July, 2025
        std::cout << (static_cast<std::chrono::year_month_day>(ymwdi) ==
                      std::chrono::July/2/2025) << '\n';
    }

Output:

    true true

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