timelocal.c

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

int main() {
    setenv("TZ", ":Europe/Berlin", 1);
    tzset();
    struct tm t = {0,21,2,25,9,98,0,0,-1};
    struct tm t_min = {0,21,1,25,9,98,0,0,-1};
    struct tm t_max = {0,21,4,25,9,98,0,0,-1};
    printf("is_dst before: %d\n", t.tm_isdst);
    // 909278460
    printf("time: %d\n", timelocal(&t));
    printf("is_dst after: %ld\n", t.tm_isdst);
    timelocal(&t_min);
    struct tm t1 = {0,21,2,25,9,98,0,0,-1};
    printf("\n\nis_dst before: %d\n", t1.tm_isdst);
    printf("%ld\n", timelocal(&t1));
    // 909274860
    printf("is_dst after: %d\n", t1.tm_isdst);
    timelocal(&t_max);
    struct tm t2 = {0,21,2,25,9,98,0,0,-1};
    // 909278460
    printf("\n\nis_dst before: %d\n", t2.tm_isdst);
    printf("%ld\n", timelocal(&t2));
    printf("is_dst after: %d\n", t2.tm_isdst);
}