How to make the datepicker display a german date format?

This seems to be a question nobody is ever asking but me: How can I get a date format like "25. Dezember 2016" instead of "25 Dezember 2016"? Right, the dot makes the difference. I use Quform, which offers already a bunch of date formats out of the box. The one I need isn't there.

Is that a datepicker js affair? How? Where? What to do?

Help urgently needed.