2010 is Twenty Ten, not Two Thousand Ten. (Someone alert They Might be Giants as we need a song like "Istanbul, not Constantinople") I don't know who decreed that (Emily Post Inc.?), but it's caught on and, if you think about it, it makes sense as it's how we always refer to dates in the past.
How do you say 1972? Nineteen Seventy Two.
When was the Norman Conquest? In One thousand Sixty Six? I think not. Ten-Sixty-Six is way catcher.
When was the War of Eighteen-Twelve? Sorry couldn't resist.
It's the Oughts (someone correct that spelling for me) that threw us off and the workaround in the past has been to use the handy, but ungrammatical "Oh." 1906 is Nineteen Oh Six.
I think the thing that make it not so obvious is that "Two thousand" and "Twenty" aren't that much different to say if you're used to saying "Two Thousand." "Twenty Oh Six" just never caught on, but it likely will in the future as the century moves forward (you heard it here probably not for the first time, but just the nth time.)
Happy Twenty Ten.