Java: Difference between two dates spanning over months

Question

I have the following code that successfully gets me the difference between two days (in days, hours, minutes, seconds):

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-DD HH:mm:ss");
Date d1 = format.parse(startTime);
Date d2 = format.parse(endTime);
long diff = d2.getTime() - d1.getTime();
long diffSeconds = diff / 1000 % 60;
long diffMinutes = diff / (60 * 1000) % 60;
long diffHours = diff / (60 * 60 * 1000) % 24;
long diffDays = diff / (24 * 60 * 60 * 1000);
System.out.println("Start: " + startTime);
System.out.println("End: " + endTime);
System.out.println(diffDays + " days, " + diffHours + " hours, " + diffMinutes + " minutes, " + diffSeconds + " seconds");

However, this does not work when the dates cross into another month, for example:

Start: 2013-07-31 10:15:01
End: 2013-08-01 11:22:33
-29 days, -22 hours, -52 minutes, -28 seconds

Start: 2013-05-31 10:15:01
End: 2013-08-01 11:22:33
-29 days, -22 hours, -52 minutes, -28 seconds

Is it possible to intelligently span over months and get accurate time differences? I am familiar with Joda but would like to stick with standard Java APIs unless this is not possible without something like Joda.

Answer 1

While you should use Joda Time simply as a much better date/time API, I suspect the problem is actually just that you're parsing the values incorrectly. Use a format string of:

yyyy-MM-dd HH:mm:ss

... with dd instead of DD. The DD value is "day in year" which I suspect is confusing things, basically overriding the month part entirely. See the SimpleDateFormat documentation for more details.

You can validate what's wrong by printing out d1 and d2 after parsing...