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

 

C++

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Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Utilities library

Language support Type support (basic types, RTTI, type traits) Library feature-test macros (C++20) Dynamic memory management Program utilities Error handling Coroutine support (C++20) Variadic functions launder (C++17) initializer_list (C++11) source_location (C++20) Three-way comparison (C++20) three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20) is_eqis_neqis_ltis_lteqis_gtis_gteq (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

General utilities Date and time Function objects Formatting library (C++20) bitset hash (C++11) integer_sequence (C++14) Relational operators (deprecated in C++20) rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_not_equalcmp_lesscmp_greatercmp_less_thancmp_greater_than (C++20)(C++20)(C++20)(C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) forward (C++11) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) apply (C++17) make_from_tuple (C++17) optional (C++17) any (C++17) variant (C++17) Elementary string conversions to_chars (C++17) from_chars (C++17) chars_format (C++17)

 

Date and time utilities

duration (C++11) time_point (C++11)	clock_time_conversion (C++20) clock_cast (C++20)
Time of day
hh_mm_ss (C++20)	is_amis_pmmake12make24 (C++20)(C++20)(C++20)(C++20)
Clocks
system_clock (C++11) steady_clock (C++11) high_resolution_clock (C++11) is_clock (C++20)	utc_clock (C++20) tai_clock (C++20) gps_clock (C++20) file_clock (C++20) local_t (C++20)
Calendars
day (C++20) month (C++20) year (C++20) weekday (C++20) operator/ (C++20) year_month_day (C++20) year_month_day_last (C++20) year_month_weekday (C++20) year_month_weekday_last (C++20)	weekday_indexed (C++20) weekday_last (C++20) month_day (C++20) month_day_last (C++20) month_weekday (C++20) month_weekday_last (C++20) year_month (C++20)
Time zones
tzdb (C++20) tzdb_list (C++20) get_tzdbget_tzdb_listreload_tzdbremote_version (C++20)(C++20)(C++20)(C++20)	time_zone (C++20) locate_zone (C++20) current_zone (C++20) zoned_time (C++20) time_zone_link (C++20) leap_second (C++20)
C-style date and time

 

std::chrono::day

Member functions

day::day

day::operator++day::operator--

day::operator+=day::operator-=

day::operator unsigned

day::ok

Nonmember functions

operator==operator<=>

operator+operator-

operator<<

from_stream

Helper classes

formatter<std::chrono::day>

 

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

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

Example

Run this code

#include <iostream>
#include <chrono>
 
int main()
{
 
    std::chrono::day d {15};
 
    d = d + std::chrono::days(2);
    if (d == std::chrono::day(17)) {
        std::cout << "Days added correctly" << "\n";
    } else {
        std::cout << "Days not added correctly" << "\n";
    }
 
    d = d - std::chrono::days(3);
    if (d == std::chrono::day(14)) {
        std::cout << "Days subtracted correctly" << "\n";
    } else {
        std::cout << "Days not subtracted correctly" << "\n";
    }
 
    std::chrono::days ds = std::chrono::day(16) - std::chrono::day(14);
    if (ds == std::chrono::days(2)) {
        std::cout << "Days subtracted correctly" << "\n";
    } else {
        std::cout << "Days not subtracted correctly" << "\n";
    }
 
}

Output:

Days added correctly
Days subtracted correctly
Days subtracted correctly

See also

operator++operator++(int)operator--operator--(int)	increments or decrements the day (public member function)
operator+=operator-=	adds or subtracts a number of days (public member function)