Yes, I know the Language & region settings panel item. But as I tried to point out, language should be English - I prefer to read user interfaces in English as they are usually rather poorly translated - but I get confused by reading 03/12/10 which for me means 3rd of December, not March 12th so I would like the dates to still be 12.03.10 with dots rather than slashes.
So currently it is the Device language setting which controls the Date format and not the Regional settings, which I just now realize is what I'm asking for. Thus I say Device language English (USA) and Regional settings Deutsch (Schweiz) should result in dd.mm.yy instead of mm/dd/yy and not only in Decimal separator and Thousands separator being changed.

Hope could clear it up what I meant...

Edit: revised text a little bit