SELF-INFLICTED Same problem as others. Installed it, used it for one day... and realized the next day it was still stuck on the 29th. Deleted the app and any trace of it I could find, removed/reinserted iCal in the dock, pasted on the icon from a recent backup copy of iCal, restarted... and five days later it was showing the 29th again. Reinstalled one last time just to try to restore the default, then re-delete.
Nice idea, but not worth this trouble. I've decided I have no problem with my iCal icon displaying iCal's original date of release (June 17) after all.
(Version 1.6)