Dupe Devil for iCal is the quick, easy way to fix duplicate entries in iCal.
Did you run into problems during your transition to the cloud? If some calendar events are appearing two or three times, or events with alarms 'magically' ended up with the same alarm multiple times, Dupe Devil is for you.
Did you restore from a backup only to find that part of your backup overlaps with existing data, and now it looks like you have to go to that long, boring meeting not once but four times next Monday? Run Dupe Devil and breath a sigh of relief.
Do you want to merge two calendars into one, but some of the same appointments are in both? Just do the merge and let Dupe Devil do the cleanup.
For maximum stability and reliability, Dupe Devil works directly with your calendars via Apple's own Calendar Framework interface; unlike other applications, it does not use 'hacks' to talk to iCal.