std::chrono::year_month_weekday_last:: 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_weekday_last
constexpr bool ok ( ) const noexcept ;
(since C++20)

Checks if this object represents a valid date. Since a year_month_weekday_last represents the last weekday of a particular month, it is valid as long as the year, month and weekday are valid.

Return value

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

Example

Run this code 
#include <cassert>
#include <chrono>
using namespace std::chrono;
 
int main()
{
    auto ymwdl{Tuesday[last]/11/2020};
    assert(ymwdl.ok());
    ymwdl = Tuesday[last]/-2/2021;
    assert(!ymwdl.ok());
    ymwdl += months(0); // Normalize month
    assert(ymwdl.ok());
}
Retrieved from " https://en.cppreference.com/mwiki/index.php?title=cpp/chrono/year_month_weekday_last/ok&oldid=161716 "