Changing language on fillable form error messages.

" it uses the UI language of the application, not of the document"

Yes, I can confirm that. It's something I use a lot.

For personalized alerts, you can only rely on the application settings:

if (app.language == "FRA") // if app language is French
{var textAlert = "Bonjour !";}
else
{var textAlert = "Hello!";}

app.alert(textAlert);

I believe it uses the UI language of the application, not of the document. If you want to have full control over it then you'll need to write your own validation and format scripts to do it, instead of relying on the built-in Date format setting.

@curtis_7372 right off the bat, I think this means the date you entered in the form field is not in the correct format (month/day/year) or is not a valid date. The error message itself tells you the correct format: mm/dd/yyyy. If the month or day is a single digit, add a leading zero (e.g., 03/08/2024).