weekdaycalc

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. Mitchell'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();

        // put a function call for weekday() here
        System.out.println("You were born on " + weekday(mm,dd,yyyy));
    }


    public static String weekday( int mm, int dd, int yyyy )
    {
        int yy, total;
        String date = "";
                //find how many years past 1900
                yy = yyyy -1900;
                //divide that by four
                total = yy/4;
                //add the last two digits, couldn't think of a better way
                if (yyyy >1999)
                    total = total +(yyyy-2000);
                if (yyyy < 2000)
                    total = total + (yyyy-1900);
                //add day to the total
                total = total+dd;
                //add month offset to the total
                total = total+month_offset(mm);
                //check for leap year and january/february
                if(mm<3 && is_leap(yyyy) == true)
                    total = total-1;
                //get the remainder
                total = total%7;
                //this is all okay, i think.
                date = weekday_name(total) + ", " + month_name(mm)+ " " + dd + ", " + yyyy;

        return date;
    }


    public static int month_offset( int month )
    {
        int result = 0;
        if(month==1)
                    result = 1;
                if(month==2)
                    result = 4;
                if(month==3)
                    result = 4;
                if(month==4)
                    result = 0;
                if(month==5)
                    result = 2;
                if(month==6)
                    result = 5;
                if(month==7)
                    result = 0;
                if(month==8)
                    result = 3;
                if(month==9)
                    result = 6;
                if(month==10)
                    result = 1;
                if(month==11)
                    result = 4;
                if(month==12)
                    result = 6;
                if(month>12)
                    result = -1;
                if(month<1)
                    result = -1;

        return result;
    }
        public static String month_name( int month )
    {
        String result = null;
        if(month == 1)
                    result = "January";
                if(month == 2)
                    result = "February";
                if(month == 3)
                    result = "March";
                if(month == 4)
                    result = "April";
                if(month == 5)
                    result = "May";
                if(month == 6)
                    result = "June";
                if(month == 7)
                    result = "July";
                if(month == 8)
                    result = "August";
                if(month == 9)
                    result = "September";
                if(month == 10)
                    result = "October";
                if(month == 11)
                    result = "November";
                if(month == 12)
                    result = "December";
                if(month > 12)
                    result = "Error";

        return result;
    }
        public static String weekday_name( int weekday )
    {
        String result = "";

        if ( weekday == 1 )
        {
            result = "Sunday";
        }
        else if ( weekday == 2 )
        {
            result = "Monday";
        }
                else if ( weekday == 3 )
                {
                        result = "Tuesday";
                }
                else if ( weekday == 4 )
                {
                         result = "Wednesday" ;
                }
                else if ( weekday == 5 )
                {
                         result = "Thursday";
                }
                else if ( weekday == 6 )
                {
                        result = "Friday" ;
                }
                else if ( weekday == 7)
                {
                         result = "Saturday" ;
                }
                else if ( weekday == 0 )
                {
                        result = "Saturday" ;
                }
                else
                {
                        result = "error";
                }
                return result;
    }

    public static boolean is_leap( int year )
    {
        // 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 ( year%400 == 0 )
            result = true;
        else if ( year%100 == 0 )
            result = false;
        else if ( year%4 == 0 )
            result = true;
        else
            result = false;

        return result;
    }
}