Defined in header <ctime>
std::tm* localtime( const std::time_t *time );

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


time - pointer to a std::time_t object to convert

Return value

pointer to a static internal std::tm object on success, or null pointer otherwise. The structure may be shared between std::gmtime, std::localtime, and std::ctime, and may be overwritten on each invocation.


This function may not be thread-safe.

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.


#include <iostream>
#include <sstream>
#include <iomanip>
#include <ctime>
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

converts time since epoch to calendar time expressed as Universal Coordinated Time
converts time since epoch to calendar time expressed as local time
C documentation for localtime

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