In case you want to delete event date(s) on teller, if there are no reservations or orders on these dates, you can select them through Administration>Events>Click on the event>go to tab Event dates>Select the ones you want to delete and click on Delete at the bottom of the page.

If the event dates cannot be deleted, due to tracking reasons, but there are no orders/reservations pending to be addressed, you can choose the event dates, using the same path as above, and click on Deactivate on site and teller. This way these dates will disappear from the website, and from teller (on New Order & Reports).

To delete a whole event, aka an event with no dates on it, you can go to Administration>Events>Click on the event and at the bottom of the General information tab of the event, you can click on Delete event.