Get Local Time Zone Offset in C under Linux

The following codes which I wrote makes use of C function calls localtime() and gmtime() to get the local time zone offset:

  1 #include <stdio.h>
  2 #include <time.h>
  3
  4 int main(int argc, char **argv) {
  5     time_t  t1, t2, base_t;
  6     double  offset = 0;
  7
  8     base_t = time(NULL);
  9     t1 = mktime(gmtime(&base_t));
 10     t2 = mktime(localtime(&base_t));
 11     offset = difftime(t2, t1);
 12
 13     printf("Local Time Zone offset = %0.3f seconds (%0.3f hours)\n", offset, offset / 3600.0);
 14
 15     return 0;
 16 }
 17