The audit log
Who did what and when, filtered by category and event.
Settings > Audit Log lists sign-ins, failed sign-ins, access changes, invitations, exports and deletes, newest first. Entries cannot be edited or removed.
Narrow it by Category, Event, Who or What and dates, then press Apply. Each row shows when it happened (in UTC), the event, who did it, what was affected, the detail and the IP address.