I believe this to be a bug. When opening my Google Calendar from my Gmail page, the translation extension automatically asks me via a dropdown if I want to translate the page, which it recognizes as English, into English. If I say Translate, it dutifully acts like it's crunching through the page, and later beams with pride that my Calendar has now been translated into English. I've ensured that Chrome has my language set to US English in both Options spots. This seems to have just started yesterday or today. 4.0.249.78 beta (36714).
