> Uwe Brauer wrote/hat geschrieben on/am 06.09.2020 14:01:
> Can't answer this, because I don't use a mail buffer, but in an org-file
> I use C-c . to insert an active time stamp (result: <2020-09-06 So>) or
> C-c ! for an inactive one (result: [2020-09-06 So])



ah you use a mail (nor message) buffer when answering this message

In any case 


I found out that 
(set-locale-environment "es_ES.UTF-8") inserts <2020-09-06 dom> 

But 
(set-locale-environment "de_DE.UTF-8") inserts <2020-09-06 Sun> 


Which is odd.