Comment by Terr_

Perhaps less a requirement and more a kind of consistency with prior limitations? For example:

1. I have events in a Calendar service.

2. I want to authorize Reminder service to see upcoming events, so that it can send reminders to attendees in a way the Calendar service does not directly support, e.g. SMS/WhatsApp.

3. With the necessary credentials/SSO, the Reminder service subscribes to Calendar and Calendar periodically POSTSs webhook updates. Reminder needs to recognize when an event is cancelled or rescheduled, so that can alter its reminders.

Do I want to give Reminder potential access to all events ever, or just ones active across the usage period? Meanwhile, the Reminder guys probably don't want to step through the whole Calendar-wide event stream to reconstruct which events haven't finally happened yet.