std::chrono::duration<Rep,Period>::operator+(unary), std::chrono::duration<Rep,Period>::operator-(unary) - cppreference.com

constexpr duration operator+() const;

constexpr std::common_type_t<duration> operator+() const;

constexpr duration operator-() const;

constexpr std::common_type_t<duration> operator-() const;

Implements unary plus and unary minus for the durations.

If rep_ is a member variable holding the number of ticks in a duration object, and D is the return type,

1) Equivalent to return D(*this);.

2) Equivalent to return D(-rep_);.

Parameters

(none)

Return value

1) A copy of this duration object.

2) A copy of this duration object, with the number of ticks negated.

Example

#include <chrono>
#include <iostream>
 
int main()
{
    constexpr std::chrono::seconds s1(-052);
    constexpr std::chrono::seconds s2 = -s1;
 
    std::cout << "Negated " << s1 << " are " << s2 << '\n';
}

See also