Hey Karl,
Thanks for reaching out to us!
To clarify here, it sounds like when you create the event you’re able to set the end date to the correct date and it displays properly on the front-end of your site. However, when you view the event on the backend it displays the wrong end date in the event settings?
As an initial step here, can you try following the Testing for Conflicts procedures to ensure there isn’t a conflict occurring within the dashboard (particularly something that could be impacting the datepicker display on the backend).
Let me know if that reveals anything new.
Thanks!