gmtime limit

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

int main() {
    time_t test;
    int last_year = 0;
    struct tm *date;
    int i;

    for(i = 1; i <= 64; i++) {
        printf("Trying gmtime(2**%d-1)\n", i);
        test = (time_t)(powl(2,i) - 1);
        date = gmtime(&test);
        if( last_year > date->tm_year ) {
            printf("Failed at %lld.  Previous year: %d.  This year: %d.\n", (long long int)test, last_year, date->tm_year);
            return 1;
        }
        else {
            last_year = date->tm_year;
        }
    }

    printf("Finished.\n");
    return 0;
}