This news story is headlined "Identical Fla. twins born in 2 separate decades." A woman gave birth to one of her sons shortly before Midnight on New Year's Year and to the second shortly after Midnight. Ergo, they say, two separate decades.
So have we given up the idea that a decade begins on the first day of a year ending in "1" and ends on the last day of a year ending in a zero? That's what I always thought, based on the simple fact that "decade" denotes ten years. So the first decade ever was years 1-10, the second was 11-20, the third was 21-30 and so on. By those rules, the current decade ends at the end of this year…but no one seems to follow this distinction.
This is not a point I care a lot about. But it seems to me like one of those things that so many people have gotten wrong that it's been redefined to suit the masses. I get the feeling the parameters for a decade have changed and I wasn't notified.