std::chrono::weekday_indexed::index(3)

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

Synopsis
   constexpr unsigned index() const noexcept; (since C++20)
   Accesses the index stored in *this.

Return value
   The index stored in *this.

Example
// Run this code
 #include <chrono>
 #include <iostream>
 int main()
 {
     std::cout << std::boolalpha;
     std::chrono::weekday_indexed wdi {std::chrono::Tuesday[2]}; // 2nd Tuesday of a month
     std::cout << (std::chrono::year_month_day{wdi/10/2019} ==
                   std::chrono::year_month_day{std::chrono::October/8/2019}) << ' ';
     wdi = {wdi.weekday()[wdi.index() + 2]}; // 2nd Tuesday => 4th Tuesday
     std::cout << (std::chrono::year_month_day{wdi/10/2019} ==
                   std::chrono::year_month_day{std::chrono::October/22/2019}) << '\n';
 }

Output:
 true true