There is a small compatibility problem between iCal and Microsoft's Entourage application when running under Snow Leopard, where upon syncing with iCal the calendar times will change to be off by a number of hours (depending on the time zone) from when they were originally created.
Apple discussion poster "teacher24_70" writes:
"I use Entourage for all of my calendar events, but then have Entourage sync with iCal and MobileMe. For some reason, the iCal times are 5 hours ahead of what they should be--and then this pushes the false times to MobileMe. The times are correct in Entourage."
This problem appears to be with how calendars are managed in Entourage, both for Office 2004 and Office 2008, and not with iCal or the Mac OS. Additionally, it seems to only be when Entourage events are synchronized to iCal, and not the other way around. The bug does not appear to be a problem with either settings or other configurations such as third-party plug-ins, since some people have had it crop up on clean installations of both OS X and Office.
Unfortunately, because of the limitations for synchronizing iPods and iPhones, people who wish to use Entourage must still go through iCal. Additionally, people using using Exchange 2003 servers must use Entourage since iCal only supports Exchange 2007 and later. As such, in order to get events to MobileMe and portable devices, the calendars will need to first be synchronized between the two programs.
Despite the availability of some workarounds and solutions, because of these conditions you will currently not be able to synchronize without this problem if you are trying to get events from an Exchange 2003 server to your iPhone or MobileMe account and use Office 2004.
Potential Solution: Update?
Some people have found that updating Office to the latest version seems to help. One user, "vondurex," updated his software sequentially from Office 12.0.0 to 12.1.0, to 12.2.0, and finally to the latest version 12.2.1 that was released a short while ago. After doing this, the problem has disappeared, and while this has worked with Office 2008, it appears the available updates for Office 2004 have not corrected this issue. Hopefully Microsoft will address this problem in Office 2004, but it may take significant recoding of the program to fix.
Workaround: use iCal...
Granted, people may like to use an alternative to iCal for their calendaring, but if you are able to solely use iCal then doing so will avoid the Entourage-to-iCal synchronization bug. For users who rely on Entourage to connect to Exchange servers, iCal in Snow Leopard can be configured for use if the server is running Exchange 2007 or later, but it does not support Exchange 2003.