Date format for exception day not working

Indeed. Above patch should do the trick.

This solved the problem, thank you! It still shows midnight (even if there are hours for the exception) but if the format chosen doesn't show time, it's ok. Maybe a different issue.

Nice.
" It still shows midnight (even if there are hours for the exception) " Can you share a screenprint of this?

The second commit was needed because both 'short' and 'long' are valid options for 'time'/'weekday' and 'date'.
And Exceptions need both:
- weekday on widget,
- date on formatter.
So I needed to break this apart, and move the 'weekday' to Slot.php, since that class is bey definition in the widget, and the value is used per slot, not per day, as in the formatter.