pdf date html in german format?

We have recently added the html code "date_format:"%d. %B %Y" to our pdfs so that our invoices autmatically display the date they were created. But today we noticed that the month is showing up in English instead of German (so "October" instead of "Oktober") We did not notice that before as September and August are the same words in bith languages. Browsing through html coding help sites it seems that "%B" should automatially show the month in the lnaguage of the system used but I cannot find anywhere in sugar to change the system to German. The only thing I can find is the timezone whcih is set correctly to Berlin. So how do I set Sugar to German?