Remove data from Database when Date reached

My users can Join events, such as ‘Reading club on Thursday’.

When my users click ‘Join’ on an events page, they are added to the database as ‘Attendees’.

I want to automatically Unjoin the users when the event date has expired.

How can I do this?

You can schedule a workflow that runs on the end date of the event + 1 (may be) and make the changes to the attendees list

Check out:

Yes so as as recommened above. For the date you can put in Events date + 7 days,
then either do “make changes to list of things” users : list of events remove Event or add it to a list of events attended or delete the entire event.
If you have 100s of users per event it may be best to within this scheduled API workflow that occurs after Event is done, to schedule an api workflow on a list of things that is all users of that event. as make changes to list of things is gneerally better for less than 50 things.