the question of how to say what year it is

OK. So far it seems to me that for the first decade, any year is expressed either as the full year, or with an "o" (pronounced "oh") and the single digit; then for the second, the prefix is "twenty-".⠀There are exceptions but that's what I seem to see.

"I graduated in twenty-ten."
"I graduated in '04."
"I graduated in twenty-sixteen."
"I graduated in two-thousand-six."
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You almost never hear stuff like this:
"I graduated in '12."
"I graduated in twenty-oh-6."