I've downloaded the latest German language file and discovered that when using old skins like "clear", the months strings show and are actually not standard German but Austrian:
January should be Januar and is Jšnner,
February should be Februar and is Feber.
(see Leo Dictionary
for reference, sorry I don't know an english-interface online dictionary, but I'm a native german).
I included an altered r2lang, maybe you could split the language (once more...) into German and German (Austria) to avoid upsetting Austrians...