From your message, I see that you are using the Jerusalem timezone. So I should probably say a few words about our current timezone support...
On Windows, the timezone labeled "Jerusalem" doesn't use daylight savings time (DST). But from the information I've seen on the internet, Jerusalem really does obey DST. So there's a discrepancy already.
Besides that, though, there's a reason why people whose machine's timezone is set to Jerusalem in Windows is seeing some other timezone name. The timezone information is equivalent, just the display name is different. And the reason why this happens is because of the browser run-time environment.
Our client application is written in JavaScript running in the browser. And within that context, the program has no way of asking the browser for the user's timezone. So we have to guess. And we guess by having a list of known timezone information (which was taken from Windows) and then run a series of calculations to find the first entry in that list that matches the browser information that we do have. In this particular case, there is another entry in the list that matches the Jerusalem timezone information but appears
before Jerusalem.
So what can we do to fix this?
Well, we could move Jerusalem in the list before the other equivalent entry. But then people in that timezone would complain that it auto-detects their timezone as "Jerusalem". Basically, you can't please everyone with this solution.
The real solution is to allow the user to specify their default timezone in the user preferences. I have opened a request for enhancement to track this feature which can be viewed at the following URL.
http://bugzilla.zimbra.com/show_bug.cgi?id=12580