constexpr bool ok() const noexcept;
(since C++20)

Determines whether this month_day stores a valid month-day combination.

The combination is valid if month() represents a valid month (month().ok() == true), unsigned{day()} >= 1, and unsigned{day()} <= D, where D is the number of days in the month represented by month(). The number of days in February is considered to be 29.

Return value

true if the month and day combination is valid, otherwise false.

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