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

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< cpp‎ | chrono‎ | weekday

constexpr std::chrono::weekday operator+(const std::chrono::weekday& wd, const std::chrono::days& d) noexcept; | (1) | (since C++20)
constexpr std::chrono::weekday operator+(const std::chrono::days& d, const std::chrono::weekday& wd) noexcept; | (2) | (since C++20)
constexpr std::chrono::weekday operator-(const std::chrono::weekday& wd, const std::chrono::days& d) noexcept; | (3) | (since C++20)
constexpr std::chrono::days operator-(const std::chrono::weekday& wd1, const std::chrono::weekday& wd2) noexcept; | (4) | (since C++20)

1-2) Adds `d.count()` days to `wd`. The weekday value held in the result is computed by first evaluating static_cast<long long>(unsigned(wd)) + d.count() and reducing it modulo 7 to an integer in the range [0, 6].
3) Subtracts `d.count()` days from `wd`. Equivalent to return wd + -d;
4) If wd1.ok() and wd2.ok() are both true, returns a std::chrono::days value `d` such that `d.count()` is in the range [0, 6] and wd2 + d == wd1. Otherwise the returned value is unspecified.

### Return value

1-3) A std::chrono::weekday holding a weekday value calculated as described above.
4) A std::chrono::days representing the distance between `wd1` and `wd2`.

### Notes

As long as the computation doesn't overflow, (1-3) always return a valid `weekday` even if wd.ok() is false.

### Example

| This section is incomplete Reason: no example

### See also

operator++operator++(int)operator--operator--(int) | increments or decrements the weekday (public member function)
operator+=operator-= | adds or subtracts a number of days (public member function)

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