std::chrono::year_month_weekday_last::operator sys_days, std::chrono::year_month_weekday_last::

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chrono I/O
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C-style date and time
constexpr operator std::chrono::sys_days ( ) const noexcept ;
(1) (since C++20)
constexpr explicit operator std::chrono::local_days ( ) const noexcept ;
(2) (since C++20)

Converts *this to a std::chrono::time_point representing the same date as this year_month_weekday_last

1) If ok() is true, returns a sys_days that represents the last weekday() of the year() and month()
2) Same as (1), but returns local_days instead of sys_days. Equivalent to local_days(sys_days( *this).time_since_epoch ( ) )

Example

#include <chrono>
#include <iostream>
using namespace std::chrono;
 
int main()
{
    constexpr auto ymwdl{Tuesday[last]/11/2021};
    static_assert(static_cast<local_days>(ymwdl) ==
                  static_cast<local_days>(November/30/2021));
    // convert from field-based to serial-based to add days
    constexpr auto sd = static_cast<sys_days>(ymwdl);
    constexpr year_month_day ymd{sd + days(42)};
    std::cout << ymd << '\n';
}

Output:

2022-01-11