So did you call 1999, 'Nineteen hundred and ninety-nine' or just 'nineteen ninety-nine'?Two thousand and ten.
2010 is a single number, it's not 20:10 or 20.10 or anything else, it's 2010.
It's like calling 23 "Two-Three".
Exactly. Even Star Trek uses the "twenty-ten" pronunciation. You never hear a character say the year is "twenty-three-thousand-thirty-four".
Not to mention we've used this type of pronunciation during the entire 20th century (nineteen-oh-one, nineteen-ten, nineteen-eighty, etc)