Edit event in frontpage as super user is only possible with release in backend

Now i created a new event in the backend and i was able to edit this event at frontend!
This means, the problem only exists with old database events taken over from JEM v2 with update to Joomla! 4 and new installation JEM 4.
Is there any solution to correct the database?

The error page shows: " Call to a member function format() on bool "

Ah, this is a known old problem: go to github.com jemproject/JEM-Project


Frontend Edit event: "Call to a member function format() on bool" if you use not english (date) #1590