#include <iostream>

int time_offset()
{   // reference:
    // https://stackoverflow.com/questions/13804095/get-the-time-zone-gmt-offset-in-c
    time_t gmt, rawtime = time(NULL);
    struct tm *ptm;

#if !defined(WIN32)
    struct tm gbuf;
    ptm = gmtime_r(&rawtime, &gbuf);
#else
    ptm = gmtime(&rawtime);
#endif
    // Request that mktime() looksup dst in timezone database
    ptm->tm_isdst = -1;
    gmt = mktime(ptm);

    return (int)difftime(rawtime, gmt);
}

int main(int argc, const char *argv[])
{
	printf("UTC offset = %d\n", time_offset()/3600);
}