std::chrono::year::operator++,std::chrono::year::operator--(3)

NAME
std::chrono::year::operator++,std::chrono::year::operator-- - std::chrono::year::operator++,std::chrono::year::operator--

Synopsis
   constexpr std::chrono::year& operator++() noexcept; (1) (since C++20)
   constexpr std::chrono::year operator++( int ) noexcept; (2) (since C++20)
   constexpr std::chrono::year& operator--() noexcept; (3) (since C++20)
   constexpr std::chrono::year operator--( int ) noexcept; (4) (since C++20)
   Adds or subtracts 1 from the year value.
   1,2) Performs *this += std::chrono::years{1};.
   3,4) Performs *this -= std::chrono::years{1};.

Parameters
   (none)

Return value
   1,3) A reference to this year after modification.
   2,4) A copy of the year made before modification.

Notes
   If the result would be outside the range [-32767, 32767], the actual stored value is
   unspecified.

Example
// Run this code
 #include <chrono>
 #include <iostream>
 int main()
 {
     std::cout << std::boolalpha;
     std::chrono::year y{2020};
     std::cout << (++y == std::chrono::year(2021)) << ' ';
     std::cout << (--y == std::chrono::year(2020)) << '\n';
     using namespace std::literals::chrono_literals;
     y = 32767y;
     y++; //← unspecified, see ↑ Notes ↑
     std::cout << static_cast<int>(y) << '\n';
 }

Possible output:
 true true
 -32768

See also
   operator+= adds or subtracts a number of years from a year
   operator-= (public member function)
   operator+ performs arithmetic on years
   operator- (function)
   (C++20)