OK, so lets settle a question – is 2020 the start of a new decade?

The thinking goes like this.

- Imagine no calendar, so you create one and of course you start the 1st year as year 1
- That means that year 10 is your 10th year and so it is not until you begin year 11 that you have started your 2nd decade.

… thus the year 2020 is the last year of the decade and not the first of a new decade … right?

### Fact Checking

According to *The Farmer’s Almanac* this is correct. Just to ensure that you believe them, they cite Jerry Seinfeld.

Yes really!

This skit is their reference …

### Does that nail it?

Nope, we need a source that is a tad more reliable. Let’s turn to an astronomer for some help. Phil Plait explains it as follows …

*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 2010s. That does indeed and in fact end today.*

*The trivial way to prove that is to ask what the date is tomorrow. It’s 1 January 2020. So yeah, no more 1 in the tens place, so the 2010s are done.*

But but but … there was no year 0, so he must be wrong.

Actually no, he is correct. The key to it is to understand this – *we don’t measure decades the same way we do centuries.*

The last day of the 21st century was indeed 31st Dec 2000 because of the year zero issue I started with. However when we talk about a decade, we refer to them as the 60s, the 70s, the 80s, and so on. We have just finished the 10s and are now into the 20s. When we think of decades then how we commonly refer to this block of 10 years does actually include the zeros. We don’t carry forward the missing year 0.

So yes, the first ever decade only had 9 years, which strictly speaking is not actually a decade. This is all driven by how we refer to these blocks of 10.

Still confused. OK try this. When you turn 30, would you ever refer to yourself as being in your 20s until you reached 31? Much as we might like to, that would never fly. The same applies to decades.

So what can I say except to perhaps now welcome you to the 20s, the start of a new decade, because it really is no longer the 10s.

Happy New Year.