playin with the time struct

i have this silly code just to see what i get from each struct member

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main()
{
    time_t mytime;
    struct tm *tmp;

    mytime = time(NULL);
    printf("local time is %s", ctime(&mytime));

    if (!(tmp = gmtime(&mytime)))
    {
        printf("UTC time not available\n");
    }
    else
    {
        printf("UTC time is %s", asctime(tmp));
        printf("%ld\n", tmp->tm_gmtoff);
        printf("hour is %d\n", tmp->tm_hour);
        printf("daylight savings is %d\n", tmp->tm_isdst);
        printf("day of the month is %d\n", tmp->tm_mday);
        printf("minuetes past the hour is %d\n", tmp->tm_min);
        printf("month is %d\n", tmp->tm_mon + 1);
        printf("seconds = %d\n", tmp->tm_sec);
        printf("day of the week is %d\n", tmp->tm_wday);
        printf("day of the year is %d\n", tmp->tm_yday);
        printf("year is %d\n", tmp->tm_year + 1900);
        printf("time zone is %s", tmp->tm_zone);
    }
    return 0;
}

---

in general i get what i expected. however daylight saving is 0 which is correct for the answers i get however how do i make it take daylight savings time into account? or is that down to the os?
The other question is what is the tm_gmtoff i just get a value 0.
coop

From a Stack Overflow answer:

tm_isdst A flag that indicates whether daylight saving time is in effect at the time described. The value is positive if daylight saving time is in effect, zero if it is not, and negative if the information is not available.