Twitter seems to be overridden by ultra-corrects telling people that today does not start a new decade because the decade begins with the year ending in a 1. They're measuring the wrong thing. The decade is the twenties. Did you enter your twenties when you turned 20 or when you turned 21? This all reminds me of the guy in 2000 who said he was tired of people saying this was Y2k because the 21st century wouldn't begin for another year, and when I tried to explain that Y2k literally stood for year 2000, he just repeated what he'd already said.
Sorry about the rant.
btw, for those who say the decades begin on the 1 year because there was no year zero, there was no year one either. The numbering system started much later.