std::chrono::year_month_weekday:: ok

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C-style date and time
std::chrono::year_month_weekday
constexpr bool ok ( ) const noexcept ;
(since C++20)

Checks if this year_month_weekday object represents a valid date.

Return value

true if this year_month_weekday object represents a valid date, that is, year ( ) . ok ( ) && month ( ) . ok ( ) && weekday_indexed ( ) . ok ( ) is true and there are at least index() weekday() s in the specified year and month. Otherwise false .

Example

Run this code 
#include <cassert>
#include <chrono>
 
int main()
{
    auto ymwdi{std::chrono::Wednesday[1]/1/2021};
    assert(ymwdi.ok());
    ymwdi = std::chrono::year(2021)/std::chrono::month(1)/std::chrono::Wednesday[42];
    assert(!ymwdi.ok());
}
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