iCal Backup 1.0.1 (Mac)
Source: Tom Sheppard
iCal Backup is an AppleScript application that backs up Apple's iCal calendar files according to user preferences. Users can select which calendars to backup, set the frequency as fast as every 5 minutes and maintain up to 999 backups per calendar. This augments your regular backup strategy by allowing you to target iCal files for backup more frequently and for fast and simple restores. iCal Backup runs as a companion to iCal and silently backs up your calendars only when the calendars have changed since the last backup. Should you ever need to restore an event, to-do or even a whole calendar you can select only the calendar you wish to restore and from what point in time. Your old calendars are not overwritten.