std::chrono::year_month_weekday::year, std::chrono::year_month_weekday::month, std::chrono::year_month_weekday::weekday, std::chrono::year_month_weekday::index, std::chrono::year_month_weekday::weekday_indexed

From cppreference.com
Date and time utilities
(C++11)
(C++11)
Clocks
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
Calendars
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
Time zones
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
C-style date and time
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::weekday weekday() const noexcept;
(3) (since C++20)
constexpr unsigned index() const noexcept;
(4) (since C++20)
constexpr std::chrono::weekday_indexed weekday_indexed() const noexcept;
(5) (since C++20)

Retrieves the field values stored in this year_month_weekday object.

Return values

1) Returns the stored std::chrono::year value.
2) Returns the stored std::chrono::month value.
3) Returns the stored std::chrono::weekday value.
4) Returns the stored weekday index.
5) weekday()[index()].