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std::chrono::year_month_day:: year, std::chrono::year_month_day:: month, std::chrono::year_month_day:: day

From cppreference.net
C++
Date and time library
std::chrono::year_month_day
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)

Retrieves the year, month and day values stored in this year_month_day object.

Return value

1) Returns the stored std::chrono::year value.
2) Returns the stored std::chrono::month value.
3) Returns the stored std::chrono::day value.

Example

Run this code 
#include <chrono>
int main()
{
    constexpr std::chrono::year_month_day ymd{std::chrono::July/1/2021};
    static_assert(ymd.year() == std::chrono::year(2021));
    static_assert(ymd.month() == std::chrono::month(7));
    static_assert(ymd.day() == std::chrono::day(1));
}