Archive completed calendar events to allow searching later

You can search for calendar events while they are in the calendar, but take them out and the application cannot see them.

If you want to export events as a files and store them prior to deleting them from Calendar you can export them by dragging and dropping an event from Calendar to a folder in Finder, but I struggle to see any purpose in this, chiefly because to see the data and the date of the event you'd have to find the right file of many with the same name (ie. Haircut) then import it back into Calendar.

I have well over a decade of events in my Calendar on my Mac and it is not a problem.

Rather than looking backwards to your previous haircut, might it be better to anticipate your next haircut by setting a recurring event in Calendar or a reminder in Reminders?