Is Java Calendar Broken??

[stuckless]

I have a weird issue with the Java calendar... and I've tested this on 2 different JVMs...

Here the test code

	public void testCalendar() {
		for (int i=0;i<24;i++) {
			Calendar c = Calendar.getInstance();
			c.set(Calendar.HOUR_OF_DAY, i);
			c.getTime(); // force field updates
			if (c.get(Calendar.HOUR_OF_DAY)!=i) {
				System.out.println("Calednar Broken for: " + i);
			} else {
				System.out.println("Calendar Pass: " + i);
			}
		}
	}

All it does is set the HOUR of the DAY to a value, and tests if that is in fact the value in the calendar.

My results are...

Calendar Pass: 0
Calendar Pass: 1
Calednar Broken for: 2
Calendar Pass: 3
Calendar Pass: 4
Calendar Pass: 5
Calendar Pass: 6
Calendar Pass: 7
Calendar Pass: 8
Calendar Pass: 9
Calendar Pass: 10
Calendar Pass: 11
Calendar Pass: 12
Calendar Pass: 13
Calendar Pass: 14
Calendar Pass: 15
Calendar Pass: 16
Calendar Pass: 17
Calendar Pass: 18
Calendar Pass: 19
Calendar Pass: 20
Calendar Pass: 21
Calendar Pass: 22
Calendar Pass: 23

This is very odd, since it would appear that it works for all cases, except 2.

If I call c.clear() before setting the HOUR of the DAY, then I get the expected results, but that defeats the purpose, since I lose the date. If create a calendar by setting all the date/time fields, it's broken again.

Can anyone confirm if the code snippet that I posted works/fails on their system?? I tried searching for bugs about this, but nothing this specific (although most people agree, the java calendar sucks).

In order to work around this... I have to do the following...

		Calendar now = Calendar.getInstance();
		// it's deprecated, but Calendar appeared broken, when seting HOUR_OF_DAY with a value of 2???
		Date d = new Date(now.get(Calendar.YEAR), now.get(Calendar.MONTH), now.get(Calendar.DAY_OF_MONTH), hr, minute, 0);
		return d.getTime();

All this because I just wanted to create a Date for a specific time of day

[Slugger]

You run that test code today and there will be no hour 2 because of daylight savings time. You run that tomorrow and I assume it'll work as expected.

[Slugger]

Quickly ported your code to a Groovy script and ran it in my JVM (1.6.0_24) and it fails for today, but succeeds for tomorrow (as expected). Your only problem is you picked one of the two bad days a year to muck around with date/calendar code. And I suspect you probably wasted a lot of time looking at your code today!

def testCal(Date d) {
        println "Testing for $d...";
        for (int i=0;i<24;i++) {
            Calendar c = Calendar.getInstance();
            c.setTime(d);
            c.set(Calendar.HOUR_OF_DAY, i);
            c.getTime(); // force field updates
            if (c.get(Calendar.HOUR_OF_DAY)!=i) {
                System.out.println("Calednar Broken for: " + i);
            } else {
                System.out.println("Calendar Pass: " + i);
            }
        }
        println "==="
}

testCal(new Date(2011 - 1900, 2, 13)); // Sun, Mar 13; start of daylight savings in North America
testCal(new Date(2011 - 1900, 2, 14)); // Mon, Mar 14; hour 2 should now exist

Testing for Sun Mar 13 00:00:00 EST 2011...
Calendar Pass: 0
Calendar Pass: 1
Calednar Broken for: 2
Calendar Pass: 3
Calendar Pass: 4
Calendar Pass: 5
Calendar Pass: 6
Calendar Pass: 7
Calendar Pass: 8
Calendar Pass: 9
Calendar Pass: 10
Calendar Pass: 11
Calendar Pass: 12
Calendar Pass: 13
Calendar Pass: 14
Calendar Pass: 15
Calendar Pass: 16
Calendar Pass: 17
Calendar Pass: 18
Calendar Pass: 19
Calendar Pass: 20
Calendar Pass: 21
Calendar Pass: 22
Calendar Pass: 23
===
Testing for Mon Mar 14 00:00:00 EDT 2011...
Calendar Pass: 0
Calendar Pass: 1
Calendar Pass: 2
Calendar Pass: 3
Calendar Pass: 4
Calendar Pass: 5
Calendar Pass: 6
Calendar Pass: 7
Calendar Pass: 8
Calendar Pass: 9
Calendar Pass: 10
Calendar Pass: 11
Calendar Pass: 12
Calendar Pass: 13
Calendar Pass: 14
Calendar Pass: 15
Calendar Pass: 16
Calendar Pass: 17
Calendar Pass: 18
Calendar Pass: 19
Calendar Pass: 20
Calendar Pass: 21
Calendar Pass: 22
Calendar Pass: 23
===

[stuckless]

You're right... I picked a bad day to play with the calendar object

So actually it's not broken, it's doing the correct thing, just that for today... there is no hour 2... damn... If I had just randomly picked a couple of other other hours for my junit test, I would have been so much further ahead

[MeInMaui]

I'm sorry, but that's hilarious.

[PLUCKYHD]

[tmiranda]

I had a laugh last night when I read this but I refrained from posting because I can imagine just how frustrated Sean must have been.

[stuckless]

It was real funny... not

Fortunately, I didn't wast too much time (but enough, none the less), on it. When it wasn't working I decided to post about it because it was baffling how hour 2 would just die... The sad thing is that it never occurred to me that i was dst related

[jptheripper]

Well, we are all really glad you posted it. Because now none of us, especially you, will ever forget

[Narflex]

This was pretty funny.