No, the new decade will not start at midnight

LOUISVILLE, Ky. — My Facebook feed has been flooded recently with friends posting their goals and dreams for the next decade. And that makes me very hopeful for them. 

I mean, if they’re setting their goals an entire year before the new decade will actually begin, clearly they have the foresight and planning skills needed to make them a reality.

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No, I’m not kidding. They have an entire year to solidify their new decade resolutions. 

The next decade won’t start until January 1, 2021.

If that feels wrong to you, don’t worry. A YouGov survey found that 64% of respondents thought 2020 would mark the start of the next decade. Even news organizations—including ABC—have been spending the last month recapping their top moments and stories of the “decade.” But, a little math tells us why our basic intuitions are misguided.

Do me a favor: count to ten. Right now, out loud or in your head, count to ten.

Now, allow me to guess that you didn’t start with zero. I’d bet a lot of money that you said, “1, 2, 3, 4…” and so on. Well, our calendar does the same the thing. It started with 1 C.E. (or A.D. 1, depending on whom you’re talking to). 

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A little further math would then tell us that the first decade spanned through 10 C.E., and the second decade started with year 11. Just the same, the first century spanned through year 100 C.E., and the second century started with year 101 C.E.

You don’t need to take my word for it. How about the Farmer’s Almanac? Or, even better, Jerry Seinfeld?

Now, I have a theory as to why so many of our intuitions tell us that the decade starts with 2020. It has to do with the way we age. When I turned 20 years old, I said I was in my 20s. And when I turn 30 in a few years, I won’t say I’m still in my 20s. That’s because, unlike our calendars, I did have a year zero (in a sense). We treat our birthdays as anniversaries of our birth—meaning, on my first birthday, I had already been alive for one year. When I was 9 years old, then, I was completing my 10th year alive.

So, for those of you born in the year 2000—yes, 2020 will mark the start of your 20s. But it won’t mark the start of the new decade.

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