AppleScript to update a busy calendar based on target calendars to show times when you're busy through a shared calendar.

UpdateBusyCalendar.scpt

on run argv
	-- Check if enough arguments are provided
	if (count of argv) < 5 then
		display dialog "Please provide the number of days to consider, minutes of margin time, the generic busy event summary, the busy calendar name, and at least one target calendar name."
		return
	end if
	
	-- Extract arguments
	set daysToConsider to item 1 of argv as number
	set marginTimeInMinutes to item 2 of argv as number
	set eventSummary to item 3 of argv
	set busyCalendarName to item 4 of argv
	set targetCalendarNames to items 5 through end of argv
	
	-- Check if the word "busy" is in the busy calendar name
	if busyCalendarName does not contain "busy" then
		display dialog "Warning: The name of the busy calendar does not contain 'busy'."
		return
	end if
	
	tell application "Calendar"
		-- Check if the busy calendar exists
		if not (exists calendar busyCalendarName) then
			display dialog "The specified busy calendar '" & busyCalendarName & "' does not exist."
			return
		end if
		set busyCalendar to calendar busyCalendarName
		
		-- Clear past events from the busy calendar
		set currentDate to current date
		set pastEvents to (every event of busyCalendar whose end date is less than currentDate)
		repeat with anEvent in pastEvents
			delete anEvent
		end repeat
		
		-- Process new and updated events in target calendars
		repeat with calendarName in targetCalendarNames
			set theCalendar to calendar calendarName
			set theEvents to (every event of theCalendar whose start date is greater than currentDate and start date is less than currentDate + daysToConsider * days)
			
			repeat with anEvent in theEvents
				log "Processing event: " & (summary of anEvent)
				
				set eventStartDate to start date of anEvent
				set eventEndDate to end date of anEvent
				
				-- Get the day of the week (1 = Sunday, 7 = Saturday)
				set dayOfWeek to weekday of eventStartDate as integer
				
				-- Get the event start and end hours
				set startHour to (hours of eventStartDate) + ((minutes of eventStartDate) / 60)
				set endHour to (hours of eventEndDate) + ((minutes of eventEndDate) / 60)
				
				-- Check if the event is during work hours on a workday
				if (dayOfWeek ≥ 2 and dayOfWeek ≤ 6) and (startHour ≥ 7 and endHour ≤ 19) then
					-- Calculate start and end times with a wide margin
					set startTime to eventStartDate - marginTimeInMinutes * 60
					set endTime to eventEndDate + marginTimeInMinutes * 60
					
					-- Create or update the busy event
					set existingBusyEvents to (every event of busyCalendar whose start date is startTime and end date is endTime)
					if (count of existingBusyEvents) is 0 then
						set busyEventProperties to {summary:eventSummary, start date:startTime, end date:endTime}
						log "Creating busy event: " & (summary of busyEventProperties)
						make new event at end of events of busyCalendar with properties busyEventProperties
					else
						log "Updating existing busy event."
						set firstEvent to item 1 of existingBusyEvents
						set summary of firstEvent to eventSummary
						set start date of firstEvent to startTime
						set end date of firstEvent to endTime
					end if
				end if
			end repeat
		end repeat
	end tell
end run