Zeller's official (asking for the day of the week)

public class Main {

    public static void main(String[] args) {
        System.out.println(calc(2018, 3, 28)); //Wednesday
        System.out.println(calc(2018, 2, 28)); //Wednesday
        System.out.println(calc(2018, 1, 28)); //Sunday
    }

    public static String calc(
            double y,
            double m,
            double d) {

        double M = 0;
        if (m < 3) {
            M = m + 12;
            y = y - 1;
        } else {
            M = m;
        }

        int C = (int) (y / 100);
        int Y = (int) (y % 100);

        double R = 0;

        if (y >= 1582) {
            R = (C / 4) - C - C;
        } else if (y >= 4) {
            R = 5 - C;
        } else {
            throw new IllegalArgumentException("year >= 4");
        }

        Double h = (d + ((26 * (M + 1)) / 10) + Y + (Y / 4) + R) % 7;

        String[] weekday = new String[] {
                "soil",
                "Day",
                "Month",
                "fire",
                "water",
                "wood",
                "Money"
        };
        return weekday[h.intValue()];

    }

}