Since updating to Joomla 4/latest Helix Ultimate (not sure which of the updates triggered it), I get an error when scheduling articles (using Start Publication) via frontend.

The error I get is: Call to a member function format() on bool As a result, I can't schedule articles.

There is not problem adding articles through frontend when publishing immediately. The error is triggered by adding a future publication date.

Any ideas on how to fix it? Thanks in advance!