std::chrono::year_month_day_last:: year, std::chrono::year_month_day_last:: month, std::chrono::year_month_day_last:: day, std::chrono::year_month_day_last:: month_day_last

From cppreference.com
Utilities library
General utilities
Relational operators (deprecated in C++20)
constexpr std:: chrono :: year year ( ) const noexcept ;
(1) (since C++20)
constexpr std:: chrono :: month month ( ) const noexcept ;
(2) (since C++20)
constexpr std:: chrono :: day day ( ) const noexcept ;
(3) (since C++20)
constexpr std:: chrono :: month_day_last month_day_last ( ) const noexcept ;
(4) (since C++20)

Retrieves the field values stored in this year_month_day_last object.

Return value

1) Returns the stored std::chrono::year value.
2) Returns the stored std::chrono::month value.
3) A std::chrono::day value corresponding to the last day of the stored year and month. If this - > ok ( ) is false , the return value is unspecified.
4) A std::chrono::month_day_last constructed from month() .

Example

#include <chrono>
 
int main()
{
    constexpr auto ymdl{std::chrono::last/11/2020};
    static_assert
    (
        ymdl.day() == std::chrono::day(30) &&
        ymdl.month() == std::chrono::November &&
        ymdl.year() == std::chrono::year(2020) &&
        ymdl.month_day_last() == std::chrono::November/std::chrono::last
    );
}