std::chrono::month_weekday::month_weekday
From cppreference.com
                    
                                        
                    < cpp | chrono | month weekday
                    
                                                            
                    | constexpr month_weekday(const std::chrono::month& m, const std::chrono::weekday_indexed& wdi) noexcept; | (since C++20) | |
Constructs a month_weekday object that stores the month m and the weekday_indexed wdi.
Notes
A more convenient way to construct a month_weekday is with operator/, e.g., std::chrono::April/std::chrono::Sunday[2].
See also
| (C++20) | conventional syntax for Gregorian calendar date creation (function) |