Date-Format in german doesn't have effect

[Rolf Schaub]

I wanna have the month name in a date in german. the following code doesn't work:

var desiredFormat = "EE. dd. MMMM yyyy";

var locale = "de_DE"

var Datum = [];

var Datumx = new(Date)

Logger.log( Utilities.formatDate(Datumx,locale,desiredFormat))

***

output: Thu. 19. January 2023

*** 

It should be Don. 19.Januar 2023. Where I'm wrong?