Converts a time value into Coordinated Universal Time (UTC).
#include <time.h> struct tm *gmtime ( const time_t *calendar);
struct tm *gmtime_r ( const time_t *calendar, struct tm *localtime);
(IN) Points to the time, in seconds since the epoch began, to convert to UTC.
(OUT) Points to a tm structure for the converted string.
Returns a pointer to a tm structure containing the time information.
The gmtime and gmtime_r functions convert the time pointed to by the calendar parameter into a broken-down time, expressed as UTC.
The structure returned is reused every time that gmtime and gmtime_r are called.
The gmtime_r function provides the same functionality as gmtime, but gmtime_r is designed for use with reentrant NLM applications. The gmtime_r function allows the caller to pass storage for the results rather than relying on per-thread data.