How do you subtract Dates in Java?

Question

My heart is bleeding internally after having to go so deep to subtract two dates to calculate the span in number of days:

    GregorianCalendar c1 = new GregorianCalendar();
    GregorianCalendar c2 = new GregorianCalendar();
    c1.set(2000, 1, 1);
    c2.set(2010,1, 1);
    long span = c2.getTimeInMillis() - c1.getTimeInMillis();
    GregorianCalendar c3 = new GregorianCalendar();
    c3.setTimeInMillis(span);
    long numberOfMSInADay = 1000*60*60*24;
    System.out.println(c3.getTimeInMillis() / numberOfMSInADay); //3653

where it's only 2 lines of code in .NET, or any modern language you name.

Is this atrocious of java? Or is there a hidden method I should know?

Instead of using GregorianCalendar, is it okay to use Date class in util? If so, should I watch out for subtle things like the year 1970?

Thanks

why do you use c3? Afaik you could leave out at least the two lines for c3 ;) — ZeissS, Aug 19 '10 at 21:43

score 49 · Accepted Answer · edited Feb 10 '14 at 14:45

49

It's indeed one of the biggest epic failures in the standard Java API. Have a bit of patience, then you'll get your solution in flavor of the new Date and Time API specified by JSR 310 / ThreeTen which is (most likely) going to be included in the upcoming Java 8.

Until then, you can get away with JodaTime.

DateTime dt1 = new DateTime(2000, 1, 1, 0, 0, 0, 0);
DateTime dt2 = new DateTime(2010, 1, 1, 0, 0, 0, 0);
int days = Days.daysBetween(dt1, dt2).getDays();

Its creator, Stephen Colebourne, is by the way the guy behind JSR 310, so it'll look much similar.

edited Feb 10 '14 at 14:45

JodaStephen

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answered Aug 19 '10 at 21:44

BalusC

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I have a small project and need it in only a few places. Coming anew from .NET, I am just a bit infuriated and frustrated at java. Thanks for the confirmation, though. – Haoest Aug 19 '10 at 22:10
1

You could also create an utility method and hide it far away in the depths of your code so that you won't be directly bothered by the ugly Calendar API ;) – BalusC Aug 19 '10 at 22:35
Did JSR 310 ever see the day ? – James P. Aug 21 '12 at 19:41
2

@James: not in Java 7. It will likely be in Java 8, see also http://blog.joda.org/2010/12/what-about-jsr-310_153.html (note: posted 4 months after this answer). I updated the links in my answer. – BalusC Aug 21 '12 at 20:10
It has been implemented in Java 8 using Period.. http://www.leveluplunch.com/java/examples/number-of-days-between-two-dates/ – galactikuh Mar 01 '15 at 18:31

score 18 · Answer 2 · answered Aug 03 '12 at 05:55

18

You can use the following approach:

SimpleDateFormat formater=new SimpleDateFormat("yyyy-MM-dd");

long d1=formater.parse("2001-1-1").getTime();
long d2=formater.parse("2001-1-2").getTime();

System.out.println(Math.abs((d1-d2)/(1000*60*60*24)));

answered Aug 03 '12 at 05:55

daniel.deng

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score 3 · Answer 3 · answered Aug 19 '10 at 21:44

3

If you deal with dates it is a good idea to look at the joda time library for a more sane Date manipulation model.

http://joda-time.sourceforge.net/

answered Aug 19 '10 at 21:44

Peter Tillemans

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score 3 · Answer 4 · answered Aug 19 '10 at 21:51

3

Well you can remove the third calendar instance.

GregorianCalendar c1 = new GregorianCalendar();
GregorianCalendar c2 = new GregorianCalendar();
c1.set(2000, 1, 1);
c2.set(2010,1, 1);
c2.add(GregorianCalendar.MILLISECOND, -1 * c1.getTimeInMillis());

answered Aug 19 '10 at 21:51

Strom

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I don't think GregorianCalendar is immutable, so if I should use c2 later again, I sort of like to have it the value as it was defined initially. – Haoest Aug 19 '10 at 22:16

score 0 · Answer 5 · edited Aug 26 '14 at 05:29

Here's the basic approach,

DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");

Date beginDate = dateFormat.parse("2013-11-29");
Date endDate = dateFormat.parse("2013-12-4");

Calendar beginCalendar = Calendar.getInstance();
beginCalendar.setTime(beginDate);

Calendar endCalendar = Calendar.getInstance();
endCalendar.setTime(endDate);

There is simple way to implement it. We can use Calendar.add method with loop. The minus days between beginDate and endDate, and the implemented code as below,

int minusDays = 0;
while (true) {
  minusDays++;

  // Day increasing by 1
  beginCalendar.add(Calendar.DAY_OF_MONTH, 1);

  if (dateFormat.format(beginCalendar.getTime()).
            equals(dateFormat.format(endCalendar).getTime())) {
    break;
  }
}
System.out.println("The subtraction between two days is " + (minusDays + 1));**

Excellent use of the word "substractation" :) – Brian Pipa Jun 20 '14 at 21:04 — Brian Pipa, Jun 20 '14 at 21:04

How do you subtract Dates in Java?

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