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

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< cpp‎ | chrono‎ | year month day

Defined in header `<chrono>` |  |
constexpr std::chrono::year_month_day operator+(const std::chrono::year_month_day & ymd, const std::chrono::months & dm) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_day operator+(const std::chrono::months & dm, const std::chrono::year_month_day & ymd) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_day operator+(const std::chrono::year_month_day & ymd, const std::chrono::years & dy) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_day operator+(const std::chrono::years & dy, const std::chrono::year_month_day & ymd) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_day operator-(const std::chrono::year_month_day & ymd, const std::chrono::months & dm) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_day operator-(const std::chrono::year_month_day & ymd, const std::chrono::years & dy) noexcept; |  | (since C++20)

1-2) Adds dm.count() months to the date represented by `ymd`. The result has the same `day()` as `ymd` and the same `year()` and `month()` as std::chrono::year_month (ymd.year(), ymd.month()) + dm.
3-4) Adds dy.count() years to the date represented by `ymd`. The result is equivalent to std::chrono::year_month_day (ymd.year() + dy, ymd.month(), ymd.day().
5) Subtracts dm.count() months from the date represented by `ymd`. Equivalent to ymd + -dm.
6) Subtracts dy.count() years from the date represented by `ymd`. Equivalent to ymd + -dy.

### Notes

Even if `ymd.ok()` is true, the resulting `year_month_day` may not represent a valid date if ymd.day() is 29, 30, or 31.

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