Difference of Dates in Java in Years

Question

Date currentDate=new Date();
DateFormat formatter=new SimpleDateFormat("dd-MM-yyyy");; 
Date date =(Date)formatter.parse(birthDate);     //birthDate is a String, in format dd-MM-yyyy
long diff = currentDate.getTime() - date.getTime();
long d=(1000*60*60*24*365);
long years = Math.round(diff / d);
age=(int) years;

The value of age is not returning right. What am I doing wrong?

Enter your birthdate: (in format dd-MM-yyyy)
25-07-1992
Current Date: Tue Apr 21 14:05:19 IST 2015
Birthday: Sat Jul 25 00:00:00 IST 1992

Output: Age is: 487

"The value of age is not returning right." For what input and what would you expect? — weston, Apr 21 '15 at 08:33
You won't get an accurate answer using this method. Use the java.time API or, if you're not using Java 8, use threetenbp — fge, Apr 21 '15 at 08:34
@weston yes, if I neglect the leap year part, the answer should still be close.. But I am getting an absurd answer — Shubharthi Dasgupta, Apr 21 '15 at 08:38

score 7 · Accepted Answer · answered Apr 21 '15 at 08:37

7

If you write long d=(1000*60*60*24*365);, the result of 1000*60*60*24*365 will be calculated as int, while this is too large for int type. You should use 1000l*60*60*24*365 to calculate this.

answered Apr 21 '15 at 08:37

locoyou

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Actually "double d=(1000*60*60*24*365.25);" would be more accurate! – James Anderson Apr 21 '15 at 09:17

weston · Answer 2 · 2017-03-03T23:43:33.843

4

It's perhaps surprising to note that you don't need to know how many days or months there are in a year or how many days are in those months, likewise, you don't need to know about leap years, leap seconds, or any of that stuff using this simple, 100% accurate method:

public static int age(Date birthday, Date date) {
    DateFormat formatter = new SimpleDateFormat("yyyyMMdd");
    int d1 = Integer.parseInt(formatter.format(birthday));
    int d2 = Integer.parseInt(formatter.format(date));
    int age = (d2-d1)/10000;
    return age;
}

edited Mar 03 '17 at 23:43

answered Apr 21 '15 at 08:46

weston

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I down voted your answer because it thought it was incorrect but I realized I was at fault and now I can't change my vote anymore. – Steve S. Jul 22 '16 at 11:47
@SteveS. thanks steve, I've just edited it, and so now you should be able to change the vote :) – weston Jul 22 '16 at 12:00

Steve Chaloner · Answer 3 · 2015-04-21T08:44:59.003

2

As well as issues mentioned in the comments above, this line causes a numeric overflow:

long d=(1000*60*60*24*365);

Remove that line, and use this instead; you'll get a roughly correct answer:

long years = Math.round(diff / 1000 / 60 / 60 / 24 / 365);

edited Apr 21 '15 at 08:44

answered Apr 21 '15 at 08:37

Steve Chaloner

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Difference of Dates in Java in Years

3 Answers3