std::chrono::year_month_day(3)

NAME
std::chrono::year_month_day - std::chrono::year_month_day

Synopsis
   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+= modifies the time point by some number of months or years
   operator-= (public member function)
   year accesses the year, month, and day stored in this object
   month (public member function)
   day
   operator sys_days converts to a std::chrono::time_point
   operator local_days (public member function)
   ok checks if the year_month_day represents a valid date
                       (public member function)
  Nonmember functions
   operator== compares two year_month_day values
   operator<=> (function)
   (C++20)
   operator+ adds or subtracts a year_month_day and some number of years or months
   operator- (function)
   (C++20)
   operator<< outputs a year_month_day into a stream
   (C++20) (function template)
   from_stream parses a year_month_day from a stream according to the provided format
   (C++20) (function template)

Helper classes
                        specialization of std::formatter that
   std::formatter<std::chrono::year_month_day> formats a year_month_day according to
   (C++20) the provided format
                        (class template specialization)

Example
// Run this code
 #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';
 }

Possible output:
 Current Year: 2021, Month: 9, Day: 5