std::gmtime - cppreference.com (original) (raw)
Converts given time since epoch as std::time_t value into calendar time, expressed in Coordinated Universal Time (UTC).
[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 this function sets errno to EOVERFLOW if it fails because the argument is too large.
[edit] Example
#include #include #include #include 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