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
                    
                                        
                    < cpp | chrono | year month weekday
                    
                                                            
                    |   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()].