getDayOfWeek

int getDayOfWeek( int d, int m, int y ) {
    int k,j;

    if (m == 1 || m == 2) {
        m += 12;
        --y;
    }
    k = y%100;
    j = y / 100;

    return ( ( ( ( d + (int)((13*(m+1))/5) + k + (int)(k/4) + (int)(j/4) + 5*j ) % 7 ) + 5 ) % 7 ) + 1;
}