Steps to reproduce

This error can be reproduced on our demo instance without much issue.

1. Change language of superuser (f.e. to German)
2. Go into app tours - edit any tour
3. Add a date into field "Date"
4. Change it to something that doesn't match the pattern (f.e. 202402-23)
5. The error message is displayed "Date format not recognized" regardless of the selected user language.

From what I can see, it seems like the error message comes from Vaadin itself and can't be modified on Magnolia's side.