std::chrono:: operator+, std::chrono:: operator- (std::chrono::day)

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< cpp ‎ | chrono ‎ | day
C++
Utilities library
General utilities
Relational operators (deprecated in C++20)
Date and time utilities
Time point
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Duration
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Clocks
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Time of day
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Calendar
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Time zone
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(C++20) (C++20) (C++20) (C++20)
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chrono I/O
(C++20)
C-style date and time
std::chrono::day
Defined in header <chrono>
constexpr std:: chrono :: day operator + ( const std:: chrono :: day & d,
const std:: chrono :: days & ds ) noexcept ;
(1) (since C++20)
constexpr std:: chrono :: day operator + ( const std:: chrono :: days & ds,
const std:: chrono :: day & d ) noexcept ;
(2) (since C++20)
constexpr std:: chrono :: day operator - ( const std:: chrono :: day & d,
const std:: chrono :: days & ds ) noexcept ;
(3) (since C++20)
constexpr std:: chrono :: days operator - ( const std:: chrono :: day & x,
const std:: chrono :: day & y ) noexcept ;
(4) (since C++20)
1,2) Adds ds. count ( ) days to d .
3) Subtracts ds. count ( ) days from d .
4) Calculate the difference, in days, between two day x and y .

Return value

1,2) std:: chrono :: day ( unsigned ( d ) + ds. count ( ) )
3) std:: chrono :: day ( unsigned ( d ) - ds. count ( ) )
4) std:: chrono :: days ( int ( unsigned ( x ) ) - int ( unsigned ( y ) ) )

Notes

1-3) If the result would be outside the range [ ​ 0 ​ , 255 ] , the actual stored value is unspecified.

Example

Run this code 
#include <cassert>
#include <chrono>
 
int main()
{
    std::chrono::day d{15};
 
    d = d + std::chrono::days(2);
    assert(d == std::chrono::day(17));
 
    d = d - std::chrono::days(3);
    assert(d == std::chrono::day(14));
 
    constexpr std::chrono::days ds = std::chrono::day(16) - std::chrono::day(14);
    static_assert(ds == std::chrono::days(2));
}

See also

increments or decrements the day
(public member function)
adds or subtracts a number of days
(public member function)
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