I don't know why calendar and date are in other language than site. In Location setting I've set Default timezone to Europe/Warsaw, Force timezone to Europe/Warsaw and Default country to Poland. In Language settings Default language is Polish, Sitewide locale is currently set on pl_PL.UTF-8 (but I also tried set this on pl_PL or jus leave empty).
I also changed locale on server to Polish.
Am I forgot about something?
it always comes to you in English? in my case my problem is that sometimes it comes out in the language that I have by default in the moodle (Spanish) and other times it comes out in English. It happens to me only with the dates that there are for the moodle (forums, weeks of a course, calendar, etc ...). There is never a defined pattern, I do not know if it has something to do with your problem.