Assignment #6

Goals:
	This lab gives students more experience in
•	Top-down design
•	Procedural abstraction using methods.
Background Information

A year with 366 days is called a leap year.  A year is a leap year if it is divisible by 4 (For example, 1996), except that it is not a leap year if it is divisible by 100 (For example, 1900); however, it is a leap year if it is divisible by 400 (for example, 2000); and there were no leap years before the introduction of the Gregorian Calendar on October 15, 1582.

Requirement:

Design an algorithm, and then write the java program to ask the user to enter a year greater than 1582. Your program then displays the following:
•	If the year is a leap year or not.
•	If the given year is a leap year, your program should then display
1.	which day of the week was Feb 29th, and
2.	the next leap year where Feb. 29th happens on the same week day.

Please note that for this assignment you should create the following two methods:
1.	The is_leap_year method, which decides if the given year is a leap year or not.
2.	The zellers method, which accepts the year, month and day and returns the weekday
(0 – 6).
3.	The display_day method which accepts the week day (0 – 6) and displays the weekday (Sunday – Saturday).

NOTE:

Use the following algorithm, known as Zeller’s Congruence, to compute a single digit, 0 to 6, for Sunday through Saturday.   For example,   22/10/1999 has occurred on Friday since the algorithm returns 5 representing Friday.

Zeller’s Algorithm

1.	Define Terms
0.1	Let  DAY an integer number representing the day of the month
0.2	Let MONTH an integer number representing the month
0.3	Let YEAR  be an integer number representing the year
0.4	Let DayNumber be the an integer number representing the day of the week( 0 represents Sunday, 6 represents Saturday)
0.5	Let StartMonth, StartYear, and LeapFactor be three integer variables used in the calculation

2.	INITIALIZE Variables
1.1	Set DAY , MONTH and YEAR to the date you want to find the week day

   3. IF MONTH < 3
		2.1 StartMonth = 0
		2.2 StartYear   = YEAR – 1

                       otherwise
		2.1 StartMonth = INT (0.4 * MONTH + 2.3)
		2.2 StartYear   = YEAR

	 4. LeapFactor = (StartYear / 4) – (StartYear / 100) + (StartYear / 400)

	 5. RETURN  DayNumber = ((365 * YEAR  + 31 * (MONTH  – 1) + DAY +  LeapFactor – StartMonth) – 1) MOD 7