I am trying to find out the proper way of speaking the year, beginning with 2010. I have found sites that give numerous opinions, but I am interested in a definitive, grammatically correct answer. It is my understanding that through 2009 it should be "two-thousand-(whatever)," but after that we should say "twenty-(whatever)." It therefore drives me crazy to hear "two-thousand-ten" or, even worse, "oh-ten." Help!
Was the year 412 "four-twelve" or "four hundred twelve"?
"four hundred twelve" is a distinct Americanism. You haven't given the most likely phrase "four hundred and twelve" which is used, I believe, everywhere else. Of course, I don't pretend to know what they called it in 412 - probably something Latin.
To the original question: Australian usage is tending towards "twenty ten", though "two thousand and ten" is also common.