Yes. It's the first thing I did hoping that it was the problem

Hello, I had the same problem, it is a bug with the isis template of the administration when updating.

You can try to change the admin template (use Hathor), after the change go to items from k2 and you will see that you can change dates.

After uploading the files from the Isis template to a clean installation of joomla, and after selecting it again in the admin all Ok.

Hi and thank you for your suggestion! It works!

The problem is just related to the template.
Anyway I hope it can fix in order to restore Isis, habor is not the best...

Hello,

Have you tried clearing your browser's cache?
Restoring the template might also do the trick.

Yes, I tried but it doesn't work