std::chrono::year_month:: ok

From cppreference.com
C++
Utilities library
General utilities
Relational operators (deprecated in C++20)
Date and time utilities
Time point
(C++11)
(C++20)
Duration
(C++11)
Clocks
(C++20)
(C++20)
(C++20)
Time of day
(C++20) (C++20)
(C++20) (C++20)
(C++20)

Calendar
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
Time zone
(C++20)
(C++20)
(C++20) (C++20) (C++20) (C++20)
(C++20)
chrono I/O
(C++20)
C-style date and time
std::chrono::year_month
constexpr bool ok ( ) const noexcept ;
(since C++20)

Checks if the year and month values stored in this object are valid.

Return value

year ( ) . ok ( ) && month ( ) . ok ( )

Example

Run this code 
#include <chrono>
using namespace std::chrono_literals;
 
int main()
{
    constexpr std::chrono::year_month ym1{3030y, std::chrono::July};
    static_assert(ym1.ok());
 
    constexpr std::chrono::year_month ym2{std::chrono::year(2020)/16};
    static_assert(!ym2.ok());
}
Retrieved from " https://en.cppreference.com/mwiki/index.php?title=cpp/chrono/year_month/ok&oldid=157412 "