@bastianallgeier und your team:
To solve the problems I would like to suggest an alternative approach:
in terms of divide and conquer, I hereby propose to separate the two pieces of information: information “date and possibly time” from the information “time zone” when entering into the Panel.
The timezone of the server and the timezone of the computer of the editor has mostly no context to the content of the page in the panel.
The information “date and possibly time” should be saved how the editor enters this in the Panel without any time shift!
In the code of the website these two fields could be combined if necessary.
It would be logical to offer a time zone input field in the panel.
What do you think?