Advenio iCal Actions has three iCal-focused Automator actions; Find Past iCal Events, Move iCal Events, and Get Date Range String from Events.
These actions can be used alone in your own workflows or combined together to achieve complex tasks as in the case of the included example workflow that archives old iCal events.
Advenio iCal Actions will help you find Past iCal Events: This action lets you search for past events based on timeframe.
Move iCal Events: This action moves the specified iCal events to the specified calendar.
Get Date Range String from Events: This action creates a date range string from the iCal events provided to it.