Is this a weird date calculation bug in groovy/java?

Question

I'm trying to calculate the number of days between two specific pairs of dates but the assert is failing on the second test, which is only a week further apart from the first test.

The code is below.

Is there a bug in my code? Or is this a weird java/groovy bug?

use(groovy.time.TimeCategory) {
    def duration = Date.parse("yyyy-MM-dd", "2013-03-10") - Date.parse("yyyy-MM-dd", "2012-12-30")
    assert duration.days == 70

    def duration2 = Date.parse("yyyy-MM-dd", "2013-03-17") - Date.parse("yyyy-MM-dd", "2012-12-30")
    assert duration2.days == 77
}

Unfortunately I do not know Groovy but may I give you and advice? Never suppose that there is a bug in java or in groovy. Your chance yo win $1 billion in lottery is higher than to find bug in those systems. — AlexR, Mar 18 '13 at 07:51
This [answer](http://stackoverflow.com/a/2757551/2024761) seemed to be good. — Rahul, Mar 18 '13 at 07:58
In whatever locale/regional settings under which this code is running, has their been a DST transition between the first date and the second? — Damien_The_Unbeliever, Mar 18 '13 at 08:12
@Damien_The_Unbeliever Yes the toString for the two dates (2nd pair) shows the start date is in EST and the end date is in EDT. I'm guessing then that the # of days calculated is exactly 1 hour short due to the transition? — Christian, Mar 18 '13 at 08:32
The above code works for me... What version of Groovy are you running? — tim_yates, Mar 18 '13 at 09:29

score 0 · Accepted Answer · answered Mar 18 '13 at 17:01

@Damien_The_Unbeliever had it right. Since EST was being used, around March, it is switched to EDT which is 1 hour ahead (so converting 2013-03-17 EDT to EST would mean it would lose one hour.)

I've changed the test to confirm that this is true. The second and third asserts pass.

use(groovy.time.TimeCategory) {
    def duration = Date.parse("yyyy-MM-dd", "2013-03-10") - Date.parse("yyyy-MM-dd", "2012-12-30")
    assert duration.days == 70

    def duration2 = Date.parse("yyyy-MM-dd", "2013-03-17") - Date.parse("yyyy-MM-dd", "2012-12-30")
    assert duration2.days == 76
    assert duration2.hours == 23
}

@Damien_The_Unbeliever truly does deserve the credit. But saying it as a comment will have to do since There's only one answer here — Christian, Jun 09 '16 at 12:27

Is this a weird date calculation bug in groovy/java?

1 Answers1