# std::chrono::month::operator+=, std::chrono::month::operator-=

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< cpp‎ | chrono‎ | month

constexpr std::chrono::month& operator+=(const std::chrono::months& m) noexcept; | (1) | (since C++20)
constexpr std::chrono::month& operator+=(const std::chrono::months& m) noexcept; | (2) | (since C++20)

Adds or subtracts `m.count()` from the month value, reducing the result modulo 12 to an integer in the range [1, 12].

1) Performs *this = *this + m;
2) Performs *this = *this - m;

### Return value

A reference to this `month` after modification.

### Notes

After a call to one of these functions, ok() is always true if no overflow occurred during the operation.

### Example

| This section is incomplete Reason: no example

### See also

operator++operator++(int)operator--operator--(int) | increments or decrements the month (public member function)
operator+operator- | performs arithmetic on `month`s (function)

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