std::chrono::operator==(std::chrono::weekday_indexed)
来自cppreference.com
                    
                                        
                    < cpp | chrono | weekday indexed
                    
                                                            
                    |   constexpr bool operator==(const std::chrono::weekday_indexed& x, const std::chrono::weekday_indexed& y) noexcept;  | 
(C++20 起) | |
比较二个 weekday_indexed x 与 y 。
返回值
x.weekday() == y.weekday() && x.index() == y.index()