It's pretty straightforward with Applescript. This script was written in OSX 10.8.3.
-- John Maisey -- www.nhoj.co.uk -- 25 Mar 2013 set myCal to "YOUR CALENDAR TITLE" -- Change the above line to your calendar's title. tell application "Calendar" tell calendar myCal set recurrence of events to "FREQ=YEARLY;INTERVAL=1" end tell end tell
Copy the above script into an Applescript Editor window, change the text between the quotes in the set myCal... line to the calendar name and press Run.