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Thread: Problems with "if " statements in terms of leap years

  1. #1
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    Default Problems with "if " statements in terms of leap years

    Hi,
    I've been working in my free time on a project which tells what day someone is born based on their birthday. However, when I start to input birthdays greater than about a year old, the program is off by about a day. I believe this problem to be due to the leap year if statement I had, which I bolded in the code below. If you can offer any tips, suggestions, or hints, that would be amazing.

    Code:
    import java.util.Scanner;
    import static java.lang.System.in;
    import static java.lang.System.out;
    public class DayOfBirth {
    	public static void main (String args[]) {
    		Scanner scanned = new Scanner (in);
    		out.println("Which year were you born?");
    		int birthYear = scanned.nextInt();
    		out.println("What month were you born?(1 for January, 2 for February...)");
    		int birthMonth = scanned.nextInt();
    		out.println("What day were you born?");
    		int birthDate = scanned.nextInt();
     
    		int daysSince = 31 - birthDate;
    		int monthsSince = 12 - birthMonth;
    		int yearsSince = 2018 - birthYear;
    		int leapYearsSince = yearsSince / 4;
    		int monthDaysSince = 0;
    		switch (monthsSince) {
    		case 0:
    			monthDaysSince = 0;//From end of December
    			break;
    		case 1:
    			monthDaysSince = 31;//November
    			break;
    		case 2:
    			monthDaysSince = 61;//October
    			break;
    		case 3:
    			monthDaysSince = 92;//September
    			break;
    		case 4:
    			monthDaysSince = 122;//August
    			break;
    		case 5:
    			monthDaysSince = 153;//July
    			break;
    		case 6:
    			monthDaysSince = 184;//June
    			break;
    		case 7:
    			monthDaysSince = 214;//May
    			break;
    		case 8:
    			monthDaysSince = 245;//April
    			break;
    		case 9:
    			monthDaysSince = 275;//March
    			break;
    		case 10:
    			monthDaysSince = 306;//February
    			break;
    		case 11:
    			monthDaysSince = 334;//January
    		}
    		String day = null;
    		int yearDaysSince = yearsSince * 365; 
    		[B]if (leapYearsSince == 0 && birthYear % 4 == 0 && birthMonth <=2) {
    			leapYearsSince++;
    		}[/B]
    		int daysSinceBirth = daysSince + leapYearsSince + monthDaysSince + yearDaysSince;
    		int daysFromMonday = daysSinceBirth % 7;
    		switch (daysFromMonday) {
    		case 0:
    			day = "Monday";
    			break;
    		case 1:
    			day = "Sunday";
    			break;
    		case 2:
    			day = "Saturday";
    			break;
    		case 3:
    			day = "Friday";
    			break;
    		case 4:
    			day = "Thursday";
    			break;
    		case 5:
    			day = "Wednesday";
    			break;
    		case 6:
    			day = "Tuesday";
    			break;
    		}
    		out.println("You were born on a " + day + ".");
    		scanned.close();
    	}
     
    }

  2. #2
    Member John Joe's Avatar
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    Default Re: Problems with "if " statements in terms of leap years

    can you explain this line?
    when I start to input birthdays greater than about a year old, the program is off by about a day.
    Whatever you are, be a good one

  3. #3
    Super Moderator pbrockway2's Avatar
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    Default Re: Problems with "if " statements in terms of leap years

    I'm having a bit of trouble following how you are calculating the birthday-of-the-week. Could you explain it (in English rather than code)? Perhaps giving an example for a specific birthday: 1 Jan, 1970 or whatever.

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