Defined in header <chrono>  

class weekday;  (since C++20)  
inline constexpr std::chrono::weekday Sunday{0};  (since C++20)  
inline constexpr std::chrono::weekday Monday{1};  (since C++20)  
inline constexpr std::chrono::weekday Tuesday{2};  (since C++20)  
inline constexpr std::chrono::weekday Wednesday{3};  (since C++20)  
inline constexpr std::chrono::weekday Thursday{4};  (since C++20)  
inline constexpr std::chrono::weekday Friday{5};  (since C++20)  
inline constexpr std::chrono::weekday Saturday{6};  (since C++20) 
The class weekday
represent a day of the week in the Gregorian calendar. Its normal range is [0, 6], for Sunday through Saturday, but it can hold any value in the range [0, 255]. Seven named constants are predefined in the std::chrono
namespace for the seven days of the week.
weekday
is a TriviallyCopyable StandardLayoutType.
constructs a weekday (public member function) 

increments or decrements the weekday (public member function) 

adds or subtracts a number of days (public member function) 

retrieves the stored weekday value retrieves ISO 8601 weekday value (public member function) 

checks if the stored weekday value is valid (public member function) 

convenience syntax for constructing a weekday_indexed or weekday_last from this weekday (public member function) 
(C++20)  compares two weekday values (function) 
(C++20)  performs arithmetic on weekday s (function) 
(C++20)  outputs a weekday into a stream (function template) 
(C++20)  parses a weekday from a stream according to the provided format (function template) 
(C++20)  specialization of std::formatter that formats a weekday according to the provided format (class template specialization) 
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