Why can't I see events older than a month?

By default, iOS only syncs a limited window of past events — and Calendar Op.2 shows exactly what the built-in iOS Calendar provides. So if older events seem to be missing, they’re almost certainly still safe; iOS just isn’t loading them yet.

Because your events are shared with the built-in iOS Calendar, widening this window in iOS settings brings them back:

1. Open the Settings app.
2. Go to Calendar › Sync.
3. Select All Events.

After a moment, your full history will appear in Calendar Op.2. This setting only changes how far back events are loaded — it never deletes anything.