how to find the time difference between GMT and Local time zone

[nagarjunasarvepalli]

i was follow one procedure,by using mktime and gmtime functions

but it is showing wrong answer..
example
1)Diff between IST and GMT 5:30 by using the aboue functions it showing 5:50

[nagarjunasarvepalli]

similarly for CDT and GMT it shows 6hrs but actually 5hrs only

[MartijnHoekstra]

Can you post your sources?
I have rough feeling that the minutes are shown in 0.5 * 100 instead of 0.5 * 60 = 30

[nagarjunasarvepalli]

thanx for the response..


0.5 * 100 instead of 0.5 * 60 = 30 may be this will happen for IST but wat about CDT instead of 5 it gives 6hrs

ok this is the sourse code..

int main() {
struct tm *tptr;
time_t secs,l_secs,gmt_secs;
float diff;
time(&secs);

tptr = localtime(&secs);
l_secs=mktime(tptr);
tptr=gmtime(&secs);
gmt_secs=mktime(tptr);
diff=l_secs-gmt_secs;


printf("difff %f",diff/3600.0);

return 1;

}

[MartijnHoekstra]

the best way to find difference is to use: difftime
also you can just make diff a time_t type.
Then to display the difference exactly, you can make use of the gmtime function and strftime to display.
See example:

time_t diff=(time_t)difftime(l_secs,gmt_secs);
char str[10]  ;
tptr=gmtime(&diff);
strftime(str, 10, "%H %M ",tptr);
 
printf("%s",str);
 

Hoping this works for you.

[MartijnHoekstra]

Oh.. and maybe also take a look at:

 tzset();

[nagarjunasarvepalli]

thanx for the reply,
still same problem
CDT and GMT diff is -5hrs only
but it show -6hrs