std::localtime

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

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) tzdb_list (C++20) get_tzdbget_tzdb_listreload_tzdbremote_version (C++20)(C++20)(C++20)(C++20) sys_info (C++20) local_info (C++20) nonexistent_local_time (C++20) ambiguous_local_time (C++20) locate_zone (C++20) current_zone (C++20) time_zone (C++20) choose (C++20) zoned_traits (C++20) 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

 

C-style date and time utilities

Functions

Time manipulation

difftime

time

clock

timespec_get (C++17)

timespec_getres (C++26)

Format conversions

asctime (deprecated in C++26)

ctime (deprecated in C++26)

strftime

wcsftime

gmtimegmtime_r (C++26)

localtimelocaltime_r (C++26)

mktime

timegm (C++26)

Constants

CLOCKS_PER_SEC

Types

tm

time_t

clock_t

timespec (C++17)

 

Defined in header <ctime>
std::tm* localtime ( const std::time_t* time );	(1)
std::tm* localtime_r( const std::time_t* time, std::tm* buf );	(2)	(since C++26)

Converts given time since epoch as std::time_t value into calendar time, expressed in local time.

1) Upon successfull conversion, the result is stored in an internal std::tm object shared between std::gmtime, std::localtime, and std::ctime and may be overwritten on each invocation.

If the returned pointer is accessed after the thread that called std::localtime that returned it has exited, the behavior is undefined.

(since C++11)

2) Upon successfull conversion, the result is stored in the std::tm object pointed to by buf.

Parameters

time

-

pointer to a std::time_t object to convert

Return value

1) A pointer to the shared internal std::tm object on success, or a null pointer on error.

2) buf on success, or a null pointer on error.

Notes

std::localtime may not be thread-safe.

(since C++11)

POSIX requires that this function sets errno to EOVERFLOW if it fails because the argument is too large.

POSIX specifies that the timezone information is determined by this function as if by calling tzset, which reads the environment variable TZ.

Example

Run this code

#include <ctime>
#include <iomanip>
#include <iostream>
#include <sstream>
 
int main()
{
    setenv("TZ", "/usr/share/zoneinfo/America/Los_Angeles", 1); // POSIX-specific
    
    std::tm tm{}; // Zero initialise
    tm.tm_year = 2020 - 1900; // 2020
    tm.tm_mon = 2 - 1; // February
    tm.tm_mday = 15; // 15th
    tm.tm_hour = 10;
    tm.tm_min = 15;
    tm.tm_isdst = 0; // Not daylight saving
    std::time_t t = std::mktime(&tm); 
    
    std::cout << "UTC:   " << std::put_time(std::gmtime(&t), "%c %Z") << '\n';
    std::cout << "local: " << std::put_time(std::localtime(&t), "%c %Z") << '\n';
}

Possible output:

UTC:   Sat Feb 15 18:15:00 2020 GMT
local: Sat Feb 15 10:15:00 2020 PST

See also

gmtimegmtime_r (C++26)	converts time since epoch to calendar time expressed as Universal Coordinated Time (function)
localtimelocaltime_rlocaltime_s (C23)(C11)	converts time since epoch to calendar time expressed as local time (function)
C documentation for localtime