Hello and welcome to the forum.
I can tell you that this isn't a Rainlendar2 bug. This was a problem on the Greek localization.
The item "%ith" was translated as "%n" instead of "%in"
(i know, this isn't a n letter but a nu Greek letter. This forum doesn't support Unicode. the %i means "here goes a number" in the C programming language)
I updated the Greek localization in the Download Language page.
The last Greek localization was from 2010-08-06. If you like Rainlendar2 and want to collaborate you can help in the translation. You can check here how: