[On Twitter recently, I saw people arguing about whether 31 December 2019 is the last day of the decade. These arguments tend to center around a confusion of what is meant by the "decade" — mostly by folks confusing this with how we define “century” (like the 20th century). But they're different! As I read these arguments I smiled; I remember seeing very similar ones 10 years ago. Back then I posted an article explaining all this, and decided to update it for the decade now ending, the 2010s. I hope this may help prevent a bar fight or two. And who knows, I may have to update it yet again in ten years… with 2020 hindsight.]
Is today the last day of the decade?
Despite arguments you might see online, the answer is: Yes. Yes, it is.
31 December 2019 is not just the last day of the year, but the last day of a decade. Now, I don't mean that in the trivial sense that any moment is the last moment of the past ten-year period — you can always talk about the last ten years that end at any time. I meant, and still mean, specifically the ...