Check if you have recently changed anything in the calendar settings.

1. Double check that you are viewing the events in the correct calendar view (Day, Week, Month).
2. Verify that the events are showing up on the correct date.
3. Confirm that the events are created with the correct time.
4. Check if auto-archiving is set in the calendar settings (which archives events before a certain date).
5. Maintain current calendar settings to ensure they are up-to-date.