Theme localization and translating dates

Hello, I purchased a premium theme: they told be it was ready for localization and that, by editing and translating a simple .po contained inside the theme folder, I would get my theme translated. This was half true because anything (or about anything) is translated except for the dates. The .po contained in the theme doesn’t have any reference to any day of the week or month: there’s nothing to translate there, nor anything related to dates. So: how do I add dates to this .po?

(oh, I contacted the theme seller, but they still don’t reply)