[naupaka]

Here's a good discussion on using launchd for timing applescripts:
http://macscripter.net/viewtopic.php?id=21367

For the applescript, paste the code into the AppleScript Editor app on you mac, and save it someplace where its location won't change. Also be sure to change the calendar name in the script to whichever calendar you use.

It will only work with OS X 10.7.2 and iOS 5, and you have to have iCloud set up on your mac and your iPhone.

hth,
naupaka