org-time-stamp in German or Spanish or....

[Uwe Brauer]

Hi 

Org-time-stamp inserts a date as specified in 
(org-time-stamp-custom-formats '(" %d.%m.%Y " . " %d.%m.%Y %a %H:%M "))

But is inserts the name of the days in English, which variable allows me
to change the language?

I thought maybe 

(defun my-set-calendar-deutsch ()               ;Version:1.190
 (interactive)
     (setq calendar-week-start-day 1
           calendar-day-name-array ["Sonntag" "Montag" "Dienstag" "Mittwoch"
                                    "Donnerstag" "Freitag" "Samstag"]))


But it does not: it steill does <2020-09-06 Sun>

What do I miss?

Thanks

Uwe Brauer