std::chrono::weekday::operator[] (3) Linux Manual Page

std::chrono::weekday::operator[] – std::chrono::weekday::operator[]

Synopsis

constexpr std::chrono::weekday_indexed operator[](unsigned index) const noexcept; (1) (since C++20)
constexpr std::chrono::weekday_last operator[](std::chrono::last_spec) const noexcept; (2) (since C++20)
1) Constructs a weekday_indexed from *this and index. The result represents the index-th weekday in some yet-to-be-specified month. If index is not in the range [1, 5] or if !ok() the values held in the result is unspecified.
2) Constructs a weekday_last from *this. The result represents the last weekday in some yet-to-be-specified month.

Return value

1) std::chrono::weekday_indexed(*this, index)
2) std::chrono::weekday_last(*this)

Example

// Run this code

#include <chrono>

#include <iostream>

using namespace std::chrono;
int main()

{
    // second tuesday in October 2019
    std::cout << year_month_day{Tuesday[2] / October / 2019y} << '\n'
              // last tuesday in October 2019
              << year_month_day{Tuesday[last] / October / 2019y} << '\n';
}

Output:

  2019-10-08
  2019-10-29