Convert time_t value to tm structure as UTC time.
  Converts timer to tm structure adjusting to UTC (formerly known as GMT) timezone.  

Parameters.

timer

pointer to a time_t value, usually returned by time function.

Return Value.
  A pointer to a tm structure.
  This structure is statically allocated and shared by gmtime, localtime and ctime functions. Each time one of these functions is called the content of the structure is overwritten.

Portability.
  Defined in ANSI-C.

Example.

/* gmtime example */
#include <stdio.h>
#include <time.h>

#define PST (-8)
#define CET (1)
#define HKG (8)

main ()
{
  time_t rawtime;
  tm * ptm;

  time ( &rawtime );

  ptm = gmtime ( &rawtime );

  printf ("Time in Los Angeles: %2d:%02d\n", ptm->tm_hour+PST, ptm->tm_min);
  printf ("Time in Berlin:      %2d:%02d\n", ptm->tm_hour+CET, ptm->tm_min);
  printf ("Time in Hong Kong:   %2d:%02d\n", ptm->tm_hour+HKG, ptm->tm_min);
  
  return 0;
}

Time in Los Angeles:  7:26
Time in Berlin:      16:26
Time in Hong Kong:   23:26

See also.
  asctime, ctime, localtime, mktime, time