Prog 96: Weekday Calculator

///Name: Ilana Levy
///Period: 5
///Program Name: Weekday Calculator
///File Name: weekdayCalculator.java
///Date Finished: 9/29/2015

import java.util.Scanner;

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

		System.out.println("Welcome to Mr. Davis's fantastic birth-o-meter!");
		System.out.println();
		System.out.println("All you have to do is enter your birth date, and it will");
		System.out.println("tell you the day of the week on which you were born.");
		System.out.println();
		System.out.println("Some automatic tests....");
		System.out.println("12 10 2003 => " + weekday(12,10,2003));
		System.out.println(" 2 13 1976 => " + weekday(2,13,1976));
		System.out.println(" 2 13 1977 => " + weekday(2,13,1977));
		System.out.println(" 7  2 1974 => " + weekday(7,2,1974));
		System.out.println(" 1 15 2003 => " + weekday(1,15,2003));
		System.out.println("10 13 2000 => " + weekday(10,13,2000));
		System.out.println();

		System.out.println("Now it's your turn!  What's your birthday?");
		System.out.print("Birth date (mm dd yyyy): ");
		int mm = keyboard.nextInt();
		int dd = keyboard.nextInt();
		int yyyy = keyboard.nextInt();

		
		System.out.println("You were born on " + weekday(mm, dd, yyyy) );
	}

public static int month_offset( int mm )
	{
		int result;
		
        if ( mm == 1 )
            result = 1;
        else if ( mm == 2 )
            result = 4;
        else if ( mm == 3 )
            result = 4;
        else if ( mm == 4 )
            result = 0;
        else if ( mm == 5 )
            result = 2;
        else if ( mm == 6 )
            result = 5;
        else if ( mm == 7 )
            result = 0;
        else if ( mm == 8 )
            result = 3;
        else if ( mm == 9 )
            result = 6;
        else if ( mm == 10 ) 
            result = 1;
        else if ( mm == 11 )
            result = 4;
        else if ( mm == 12 )
            result = 6;
        else 
            result = -1;
		
		return result;
	}
public static boolean isLeap( int yyyy )
            {
                // years which are evenly divisible by 4 are leap years,
                // but years divisible by 100 are not leap years,
                // though years divisible by 400 are leap years
                boolean result;

                if ( yyyy%400 == 0 )
                    result = true;
                else if ( yyyy%100 == 0 )
                    result = false;
                else if ( yyyy%4 == 0 )
                    result = true;
                else
                    result = false;

                return result;
            }    
	public static String weekday( int mm, int dd, int yyyy )
	{
		int yy, total, day;
		String date = "";
            yy = yyyy - 1900;
        total = yy/ 4 + yy + month_offset(mm) + dd;
        
        if ( isLeap(yyyy) == true && mm == 1 )
            total = total - 1;
        
        else if ( isLeap(yyyy) == true && mm ==2 )
                total = total -1 ;
        
		// bunch of calculations go here
        day = total % 7 ;
        
		date = weekday_name(yyyy,mm,dd) + ", " + mm  + " " + dd + ", " + yyyy;

		return date;
	}

    
    public static String weekday_name(int yyyy, int mm, int dd)   
    {
        		int yy, total, day;
		String date = "";
            yy = yyyy - 1900;
        total = yy/ 4 + yy + month_offset(mm) + dd;
        
        if ( isLeap(yyyy) == true && mm == 1 )
            total = total - 1;
        
        else if ( isLeap(yyyy) == true && mm ==2 )
                total = total -1 ;
        
		// bunch of calculations go here
        
        String Day;
        day = total % 7;
        
        if ( day == 1 )
            Day = "Sunday";
        else if ( day == 2 )
            Day = "Monday";
        else if ( day == 3 )
            Day = "Tuesday";
        else if ( day == 4 )
            Day = "Wednesday";
        else if ( day == 5 )
            Day = "Thursday";
        else if ( day == 6 )
            Day = "Friday";
        else if ( day == 7 )
            Day = "Saturday";
        else
            Day = "error";
        
        
        return Day;
    }


	// paste your functions from MonthName, WeekdayName, and MonthOffset here
		
	
    

}