std::chrono::year_month_day

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

The class year_month_day represents a specific year, month, and day. It is a field-based time point, with a resolution of std::chrono::days. std::chrono::years- and std::chrono::months-oriented arithmetic are supported directly. An implicit conversion to and from std::chrono::sys_days allows std::chrono::days-oriented arithmetic to be performed efficiently.

year_month_day is a TriviallyCopyable StandardLayoutType.

Member functions

(constructor)	constructs a `year_month_day` (public member function)
operator+=operator-=	modifies the time point by some number of months or years (public member function)
yearmonthday	accesses the year, month, and day stored in this object (public member function)
operator sys_daysoperator local_days	converts to a `std::chrono::time_point` (public member function)
ok	checks if the `year_month_day` represents a valid date (public member function)

Nonmember functions

operator==operator<=> (C++20)	compares two `year_month_day` values (function)
operator+operator- (C++20)	adds or subtracts a `year_month_day` and some number of years or months (function)
operator<< (C++20)	outputs a `year_month_day` into a stream (function template)
from_stream (C++20)	parses a `year_month_day` from a stream according to the provided format (function template)

Helper classes

std::formatter<std::chrono::year_month_day> (C++20)	formatting support for `year_month_day` (class template specialization)
std::hash<std::chrono::year_month_day> (C++26)	hash support for `std::chrono::year_month_day` (class template specialization)

Example

#include <chrono>
#include <iostream>

int main()
{
    const std::chrono::time_point now{std::chrono::system_clock::now()};

    const std::chrono::year_month_day ymd{std::chrono::floor<std::chrono::days>(now)};

    std::cout << "Current Year: " << static_cast<int>(ymd.year()) << ", "
                 "Month: " << static_cast<unsigned>(ymd.month()) << ", "
                 "Day: " << static_cast<unsigned>(ymd.day()) << "\n"
                 "ymd: " << ymd << '\n';
}

Possible output:

Current Year: 2023, Month: 9, Day: 4
ymd: 2023-09-04

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