Cloning Events Manager data

(This is tangentially related to my previous Zapier post).

Zapier can’t see the event dates created by Events Manager, but Zapier can see data in custom fields created by the Advanced Custom Fields plugin.

What I’d therefore like to do is, every time a event is created in Events Manager, simply clone/copy that event date information into a Custom Field.

I suspect that’s hooking into some function used by Events Manager when it saves the event, but I don’t quite know enough to know which function, or quite how to do that?