Timezone information in C (offset, names, etc)

#include<time.h>
#include<stdio.h>
#include <stdlib.h>
#include <string.h>
 
/*
  can be called in shell with:
 
  shell$ TZ="Europe/Rome" ./teste
 
 */
 
int main(int argc, char *argv[])
{
    time_t now_time;
    struct tm *now;
 
    // Forcing timezone
 
    //setenv("TZ", "Europe/Rome", 1);
    //tzset();
 
    time(&now_time);
    printf("Now (unix timestamp): %ld \n\n", now_time);
 
    now = localtime(&now_time);
 
    printf(">>>> Now (gmt offset %ld): %s\n", now->tm_gmtoff, asctime(now));
    printf(">>>> isDst: %d\n", now->tm_isdst);
    printf(">>>> tzname: %s\n", now->tm_zone);
 
 
    return 0;
}