std::chrono::year::year(3)

NAME
std::chrono::year::year - std::chrono::year::year

Synopsis
   year() = default; (1) (since C++20)
   explicit constexpr year( int y ) noexcept; (2) (since C++20)
   Constructs a year object.
   1) Default constructor leaves the year value uninitialized.
   2) If y is in the range [-32767, 32767], constructs a year object holding the year
   value y. Otherwise the value held is unspecified.

Example
// Run this code
 #include <chrono>
 #include <iostream>
 int main() {
     using namespace std::chrono;
     constexpr int leap_years = [] {
         int count{};
         for (int i{year::min()}; i <= int{year::max()}; ++i)
             if (year{i}.is_leap()) // uses constructor (2)
                 ++count;
         return count;
     } ();
     static_assert(15891 == leap_years);
     std::cout << "There are " << leap_years << " leap years in the range ["
               << int(year::min()) << ", " << int(year::max()) << "].\n";
 }

Output:
 There are 15891 leap years in the range [-32767, 32767].