JS Date - JS Engine bug, or I'm losing my mind?!

[jodishowers]

Greetings all. My 1st post here - hoping someone can help out.

First I've tested this on FF 1.5.0.9, 2.x and Safari on OSX.

here's the code that exhibits the behaviour:

#case 1 - fails
var date1 = new Date();
date1.setYear(2 007);
date1.setMonth( 3);
date1.setDate(1 0);
alert('(2007-3-10) ::' + date1.getFullYe ar() + '-' + (date1.getMonth ()) + '-' + date1.getDate() ); // 2007-4-10
alert('(April 10, 2007) ::' + date1.toDateStr ing()); #Thu May 10 2007

#case 2 - succeeds - expected behaviour
var date2 = new Date();
date2.setYear(2 007);
date2.setMonth( 4);
date2.setDate(1 2);
alert('(2007-4-12) ::' + date2.getFullYe ar() + '-' + (date2.getMonth ()) + '-' + date2.getDate() ); // 2007-4-12
alert('(May 12, 2007) :: ' + date2.toDateStr ing()); // #Sat May 12 2007

So I'm seeing a nasty behaviour:
date1.setMonth + 1 == date1.getMonth

I've only seen this happen for month 3 (April).

Am I losing my mind (perhaps the wrong group)? Or can someone help me identify what's missing in my logic - because it would be unusual if a bug was identical across browsers (unless the JS engine is the same in both FF and Safari in osx).

I'll try IE Windows next.

TIA!
Jodi

[Motoma]

Here is a better explanation of why the error is occurring.

When you call new Date(), your date is initialized to today. You then go and change the year, month, then day:

January 31 2007
Doesn't change when updating the year:
January 31 2007
then it becomes:
April 31 2007
Which doesn't exist, therefor it rolls over to:
May 31 2007
and then you update the day:
May 10 2007

Hope this makes sense...it took me a moment to figure out.

[acoder]

If you look at my code, you can specify the month and date with setFullYear().

Beat me to it!

[jodishowers]

Motoma - yes. Now I understand.

When I read "works for me" I thought you were referring to my code sample where I:

 date1.setFullYear(2007);
 

Upon re-reading I see you coded as

 date1.setFullYear(2007,3,10);
 

yes. that's a workable approach. Not a very good name for a method call IMO (setFullYear).

How about JS testing frameworks? I'm looking at scriptaculous Test.Unit (http://wiki.script.acu lo.us/scriptaculous/show/Test.Unit.Runne r).

Thanx for you help.
Jodi