Translating recurring-invoice variables like :MONTH possible?

Hi guys,
first, i just switched to invoiceninja and I am already a huge fan, thanks so much.

Now the only problem I am facing is the variables in recurring invoices ( :MONTH etc )being always in english language, although my customers are all speaking german.
Did I miss anything?
Or could you give me a hint on where about I have to change things in code to make this happen?
(Im using the self-hosted version and I am a Developer so this should be no problem, just wanted to ask first)


I think this change should help