[TYPO3-ttnews] localize date

[Chhengleap SOEM]

Dear all,

I want to localize date in the Extension News but I can't. Example: 
<f:format.date format="d.F.Y">{newsItem.datetime}</f:format.date>
result: 20.December.2011 but when I switch language to de it doesn't 
localize to 20.Dezember.2011.
How can I do that? Any one has ideas to deal with this problems.

Best regards,

Chhengleap