(Science: day of the week) Zeller’s congruence is an algorithm developed by Christian Zeller to calculate the day of the week. The formula is

/*
(Science: day of the week) Zeller’s congruence is an algorithm developed by
Christian Zeller to calculate the day of the week.
*/
import java.util.Scanner;

public class Exercise_03_21 {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);

		// Prompt the user to enter a year, month, and day of the month.
		System.out.print("Enter year: (e.g., 2012): ");
		int year = input.nextInt();
		System.out.print("Enter month: 1-12: ");
		int month = input.nextInt();
		System.out.print("Enter the day of the month: 1-31: ");
		int dayOfMonth = input.nextInt();

		// Convert January and February to months 13 and 14 of the previous year
		if (month == 1 || month == 2)
		{
			month = (month == 1) ? 13 : 14;
			year--;
		}

		// Calculate day of the week
		int dayOfWeek = (dayOfMonth + (26 * (month + 1)) / 10 + (year % 100) 
				+ (year % 100) / 4 + (year / 100) / 4 + 5 * (year / 100)) % 7; 

		// Display reslut
		System.out.print("Day of the week is ");
		switch(dayOfWeek)
		{
			case 0: System.out.println("Saturday"); break;
			case 1: System.out.println("Sunday"); break;
			case 2: System.out.println("Monday"); break;
			case 3: System.out.println("Tuesday"); break;
			case 4: System.out.println("Wednesday"); break;
			case 5: System.out.println("Thursday"); break;
			case 6: System.out.println("Friday");
		}
	}
}