Recently, once of our Exchange users encountered an odd error while trying to use iCal to save a calendar event to our Exchange 2010 server. When trying to save a new event, the following error would crop up:

iCal can’t save the event “whatever the event name is” to the Exchange server.

The account *****@*****.**** currently can’t be modified. To discard your changes and continue using the version of your calendars that’s on the server, click Rever to Server. To save your changes on your computer until the problem is resolved, click Go Offline.

(Go Offline)     (Revert to Server) (Try Again)

Weird, eh?

After doing a bit of digging, we quickly found the issue documented here and there on the web. It seems that the problem stems from the fact that iCal does not by default use the system settings for Time Zones, and the above error pops up if there is a mismatch.

To fix the issue, it is necessary to go to the Advanced tab of the iCal preferences (iCal -> Prefererences -> Advanced) and enable time zone support. Also, check the system’s time zone settings (System Preferences -> Date & Time -> Time Zone) and make sure that the correct time zone is set there.