Defined in header <chrono>
class year_month_day_last;
(since C++20)

The class year_month_day_last represents the last day of a specific year and month. It is a field-based time point, with a resolution of std::chrono::days, subject to the limit that it can only represent the last day of a month.

std::chrono::years- and std::chrono::months-oriented arithmetic are supported directly. An implicit conversion to std::chrono::sys_days allows std::chrono::days-oriented arithmetic to be performed efficiently.

year_month_day_last is a TriviallyCopyable StandardLayoutType.

Member functions

constructs a year_month_day_last object
(public member function)
modifies the time point by some number of months or years
(public member function)
accesses the fields of this object
(public member function)
converts to a std::chrono::time_point
(public member function)
checks whether this object represents a valid date
(public member function)

Nonmember functions

compares two year_month_day_last values
adds or subtracts a year_month_day_last and some number of years or months
outputs a year_month_day_last into a stream
(function template)

Helper classes

specialization of std::formatter that formats a year_month_day_last according to the provided format
(class template specialization)


#include <iostream>
#include <chrono>
// until online compiler supports streaming the year_month_day_last:
std::ostream& operator<< (std::ostream& os, std::chrono::year_month_day_last ymdl) {
    return os << static_cast<int>(ymdl.year()) << '/' 
              << static_cast<unsigned>(ymdl.month()) << '/'
              << static_cast<unsigned>(ymdl.day());
int main()
    const auto ymd = std::chrono::year_month_day{
    const std::chrono::year_month_day_last ymdl{
        ymd.year(), ymd.month() / std::chrono::last
    std::cout << "The date of the last day of this month is: " << ymdl << '\n';
    // The `last` object can be places wherever it is legal to place a `day`:
    using namespace std::chrono;
    constexpr std::chrono::year_month_day_last
        ymdl1 = 2023y / February / last,
        ymdl2 = last / February / 2023y,
        ymdl3 = February / last / 2023y;
    static_assert( ymdl1 == ymdl2 and ymdl2 == ymdl3 );

Possible output:

The date of the last day of this month is: 2021/11/30

See also

represents a specific year, month, and day

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