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

std::chrono::year::operator+, std::chrono::year::operator- - cppreference.com

From cppreference.com

`constexpr std::chrono::year operator+() noexcept;`	(1)	(since C++20)
`constexpr std::chrono::year operator-() noexcept;`	(2)	(since C++20)

Applies the unary operators to the year value.

1) Returns a copy of *this.

2) Returns a year whose year value is the negation of that of *this.

Return value

1) *this

2) std::chrono::year(-int(*this))

Example

#include <chrono>
#include <iostream>

int main()
{
    constexpr std::chrono::year y{2020};
    constexpr auto ny = -y;
    std::cout << "The year " << (int)y << " negated is " << (int)ny << '\n';
}

Output:

The year 2020 negated is -2020