std::difftime

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Date and time library
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Date and time library

Time point
time_point (C++11)
clock_time_conversion (C++20)
clock_cast (C++20)
Duration
duration (C++11)
Clocks
system_clock (C++11)
steady_clock (C++11)
is_clock (C++20)
utc_clock (C++20)
tai_clock (C++20)
high_resolution_clock (C++11)
gps_clock (C++20)
file_clock (C++20)
local_t (C++20)
Time of day
is_amis_pm (C++20)(C++20)
make12make24 (C++20)(C++20)
hh_mm_ss (C++20)

Calendar
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)
last_speclast (C++20)(C++20)
`chrono` I/O
parse (C++20)

Time zone
tzdb (C++20)
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choose (C++20)
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zoned_time (C++20)
time_zone_link (C++20)
leap_second (C++20)
leap_second_info (C++20)
get_leap_second_info (C++20)
C-style date and time

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C-style date and time utilities

Functions
Time manipulation
difftime
time
clock
timespec_get (C++17)
Format conversions
asctime
ctime
strftime
wcsftime
gmtime
localtime
mktime
Constants
CLOCKS_PER_SEC
Types
tm
time_t
clock_t
timespec (C++17)

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Defined in header`<ctime>`
double difftime(std::time_t time_end,std::time_t time_beg);

Computes difference between two calendar times asstd::time_t objects (time_end- time_beg) in seconds. Iftime_end refers to time point beforetime_beg then the result is negative.

[edit]Parameters

time_beg, time_end

times to compare

[edit]Return value

Difference between two times in seconds.

[edit]Notes

On POSIX systems,std::time_t is measured in seconds, anddifftime is equivalent to arithmetic subtraction, but C and C++ allow fractional units fortime_t.

[edit]Example

Run this code

#include <ctime>#include <iostream> int main(){std::time_t start=std::time(nullptr);volatiledouble d=1.0; // some time-consuming operationfor(int p=0; p<10000;++p)for(int q=0; q<100000;++q)            d= d+ p* d* q+ d; std::cout<<"Wall time passed: "<< std::difftime(std::time(nullptr), start)<<" s.\n";}