One-way sync two calendars within OS X Calendar app. In this case, used to move events from an Exchange account to an iCloud account.

CalSync

property today : current date
property bfCal : "*NAME OF SOURCE CALENDAR*"
property iCal : "*NAME OF DESTINATION CALENDAR*"

-- used for Growl notification
property allNotifications : {}

tell application "Calendar" to launch
tell application "Calendar" to reload calendars
-- wait for reload to happen
delay 30

tell application "Calendar"
	
	set iEvents to events of calendar iCal
	set bfEvents to events of calendar bfCal
	
	-- delete existing events in source calendar
	repeat with calEvent in iEvents
		delete calEvent
	end repeat
	
	repeat with calEvent in bfEvents
	  -- copy over all recurring events
		if recurrence of calEvent is not missing value then
			copy calEvent to end of events of calendar iCal
		-- otherwise, only copy events occuring today or in the future
		else if start date of calEvent ≥ today then
			copy calEvent to end of events of calendar iCal
		end if
	end repeat
	
end tell

-- trigger Growl notification
growl("CalSync", "Calendars have been syncd")

on growl(theTitle, theContent)
	if allNotifications does not contain theTitle then
		set allNotifications to allNotifications & theTitle
	end if
	set myName to path to me as text
	set TID to text item delimiters
	set text item delimiters to ":"
	set myName to the last text item of myName
	set text item delimiters to TID
	tell application id "com.Growl.GrowlHelperApp"
		register as application myName ¬
			all notifications allNotifications ¬
			default notifications allNotifications ¬
			icon of application "Calendar"
		notify with name theTitle ¬
			title theTitle ¬
			description theContent ¬
			application name myName
	end tell
end growl