std::chrono::weekday_indexed(3)

NAME
std::chrono::weekday_indexed - std::chrono::weekday_indexed

Synopsis
   Defined in header <chrono>
   class weekday_indexed; (since C++20)
   The class weekday_indexed combines a weekday, representing a day of the week in the
   proleptic Gregorian calendar, with a small index n in the range [1, 5]. It
   represents the first, second, third, fourth, or fifth weekday of some month.
   weekday_indexed is a TriviallyCopyable StandardLayoutType.

Member functions
   constructor constructs a weekday_indexed
                 (public member function)
   weekday access the stored weekday
                 (public member function)
   index access the stored index
                 (public member function)
   ok checks if the weekday and index are both valid
                 (public member function)
   Nonmember functions
   operator== compares two weekday_indexed values
   (C++20) (function)
   operator<< outputs a weekday_indexed into a stream
   (C++20) (function template)

Helper classes
   std::formatter<std::chrono::weekday_indexed> formatting support for weekday_indexed
   (C++20) (class template specialization)
   std::hash<std::chrono::weekday_indexed> hash support for
   (C++26) std::chrono::weekday_indexed
                        (class template specialization)

Example
// Run this code
 #include <chrono>
 #include <iostream>
 int main()
 {
     using namespace std::chrono;
     constexpr weekday_indexed wi = Friday[2];
     // Indexed weekday can be used at any place where chrono::day can be used:
     constexpr year_month_weekday ymwd = 2021y / August / wi;
     static_assert(ymwd == August / wi / 2021y &&
                   ymwd == wi / August / 2021y);
     std::cout << ymwd << '\n';
     constexpr year_month_day ymd{ymwd}; // a conversion
     static_assert(ymd == 2021y / 8 / 13);
     std::cout << ymd << '\n';
 }

Possible output:
 2021/Aug/Fri[2]
 2021-08-13