Is it possible to hide completed events from my calendar?

Yes, it is possible.
Follow these steps to hide complete events from your calendar.

1. Click the User Menu on the top right corner of the screen.
2. Click the Settings button.
3. Look for the My Preferences section.
4. Select Calendar Settings.
5. Click the Edit icon on the top right.
6. Enable the Hide completed calendar events checkbox.
7. Click Save.

To learn more about Calendar Settings, click here.