std::chrono::weekday::weekday
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                    |   weekday() = default;  | 
(1) | (since C++20) | 
|   explicit constexpr weekday(unsigned wd) noexcept;  | 
(2) | (since C++20) | 
|   constexpr weekday(const std::chrono::sys_days& dp) noexcept;  | 
(3) | (since C++20) | 
|   explicit constexpr weekday(const std::chrono::local_days& dp) noexcept;  | 
(4) | (since C++20) | 
Constructs a weekday object.
1) Default constructor leaves the weekday value uninitialized.
2) Constructs a 
weekday object holding the weekday value wd. If wd > 255, the value held is unspecified.3) Constructs a 
weekday object representing the day of the week dp corresponds to. This constructor defines an implicit conversion from std::chrono::sys_days to weekday.4) Constructs a 
weekday object representing the day of the week dp corresponds to, as if by weekday(std::chrono::sys_days(dp.time_since_epoch())).