You can enable/disable calendars on your thank you page and countdown pages on our end.

To do so, go to event editor.

Click on "Customize". 

To enable/disable calendar for thank you page, click on "Configure" for "Thank You For Registering Page".

To enable/disable calendar for countdown page, click on "Configure" for "Countdown Page".

This is how the calendar icon looks like on those pages:
​