Sadly, that is incorrect. Decades start at year zero. When you hit 01, you have completed the first year of the decade. I know that seems weird, but it's a fact. It's like your life, after your first year you were one year old...you didn't start out a year old. Didn't your teacher tell you not to count with your fingers?I'll never pass up a chance to hear Jimi play, but . . .
Neither Jan. 1, 1970 nor now is "entering a new decade."
Groups of ten's start at "1," not zero. They end at zero.
Just look at your fingers ... one, two, three ...