Comparing if two Date instances refer to the same day

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+2 Q:

Comparing if two Date instances refer to the same day

I have two Java instances of java.util.Date and I have to find out if they refer to the same day.

I can do this the hard way, taking the dates apart and compare the days, making sure the years match too.

Since this is such a common problem, I expect there to be an easier solution to this problem.

Thanks!

+1 A:

I use the DateUtils by Apache, it provides the isSameDay(Date,Date) method.

jnt30 2009-09-10 16:53:23

If that's the signature and there's no time zone context anywhere else, then it is necessarily broken (or at least restricted to work in an assumed time zone).

Jon Skeet 2009-09-10 16:56:25

(The fact that the Javadocs don't even mention which zone is used would make me highly nervous about using that class at all, to be honest. Joda Time is simply a better choice, IMO.)

Jon Skeet 2009-09-10 16:59:40

+4 A:

Instances of java.util.Date refer to instants in time. Which day they fall on depends on which time zone you're using. You could use a java.util.Calendar to represent an instant in a particular time zone...

... or you could use Joda Time instead, which is a much, much better API. Either way, you'll have to know what time zone you're interested in.

In Joda Time, once you've got a relevant time zone, you can convert both instants to LocalDate objects and compare those. (That also means you can compare whether instant X in time zone A is on the same day as instant Y in time zone B, should you wish to...)

Jon Skeet 2009-09-10 16:53:50

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Comparing if two Date instances refer to the same day

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