days_between

#include <stdio.h>
#include <stdlib.h>

int days_between (int d1, int m1, int y1, int d2, int m2, int y2)
{
    int result;
    int n1;
    int n2;

    if(m1 > 2)
        m1 = m1+1;
    else
    {
        m1 = m1 + 13;
        y1 = y1 - 1;
    }

    n1 = 36525 * y1 / 100 + 306 * m1 / 10 + d1;

    if(m2 > 2)
        m2 = m2+1;
    else
    {
        m2 = m2 + 13;
        y2 = y2 - 1;
    }

    n2 = 36525 * y2 / 100 + 306 * m2 / 10 + d2;
    result = n2 - n1;
    return result;
}

/* проверить можно на http://www.goroskop.org/horoscope/daycal/form1.shtml */
int main (void)
{
    printf("%d\n",days_between(23,2,1984, 23,8,2010));
    system("pause");
    return 0;
}