Defined in header <ctime> | ||
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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).
| time | - | pointer to a time_t object to convert |
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.
#include <iostream>
#include <sstream>
#include <iomanip>
#include <ctime>
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
| converts time since epoch to calendar time expressed as local time (function) |
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C documentation for gmtime |
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