std::gmtime
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Defined in header
<ctime>
std::tm * gmtime( const std::time_t * time );
Converts given time since epoch as std::time_t value into calendar time, expressed in Coordinated Universal Time (UTC).
Contents
[edit] Parameters
time
-
pointer to a time_t object to convert
[edit] 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.
[edit] Notes
This function may not be thread-safe.
POSIX requires that gmtime sets errno to EOVERFLOW if it fails because the argument is too large.
[edit] Example
Run this code
#include <ctime> #include <iomanip> #include <iostream> #include <sstream> int main() { setenv("TZ", "/usr/share/zoneinfo/Europe/London", 1); // POSIX-specific std::tm tm{}; // get_time does not set all fields hence {} tm.tm_year = 2020 - 1900; // 2020 tm.tm_mon = 7 - 1; // July tm.tm_mday = 15; // 15th tm.tm_hour = 10; tm.tm_min = 15; tm.tm_isdst = 1; // Daylight saving in London 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: Wed Jul 15 09:15:00 2020 GMT local: Wed Jul 15 10:15:00 2020 BST
[edit] See also
C documentation for gmtime