I have an SPO library with a Retention Policy attached for archiving items over 3 months old. The policy is attached to the location, not the content type, and is set to run when a field (Arrival Date) is +3 months, whereupon it engages a workflow which copies the item to another library, then deletes the original.
My question is: how can I tell when the timer job that kicks off the retention steps has run? I seem to remember it's about once a week per site collection, but need to know exactly how to get this for support documentation and handover.