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

int calc_date(int *y, int *m, int *d, int n)
{
    struct tm t = { 0 };

    t.tm_year = *y - 1900;
    t.tm_mon  = *m - 1;
    t.tm_mday = *d + n;
    if (mktime(&t) == -1) return 0;
    *y = t.tm_year + 1900;
    *m = t.tm_mon + 1;
    *d = t.tm_mday;
    return 1;
}

int main()
{
    int y = 2002, m = 8, d = 8;

    if (calc_date(&y, &m, &d, -3))
        printf("%4d/%02d/%02d\n", y, m, d);
    return 0;
}