2 Comments »Posted on Tuesday 12 January 2010 at 8:23 pm by Jacob Aron
In Getting It Wrong, Mathematics

Hello! It’s 2010, and I’m finally back. I had intended an earlier return to blogging here at Just A Theory, but unfortunately a rather serious computer failure held me up. The hard drive in my PC died, causing Windows to become corrupt and refuse to boot. As you can see, I attempted some minor brain surgery in an effort to revive the poor machine:

I actually had some success, and after more than 12 hours of work was rewarded with this rather understated error message:

Quite. Sadly, in the end I had to say goodbye to my faithful old PC and buy a new one, complete with Microsoft’s latest operating system, Windows 7. It’s quite different to the Windows XP I’m used to, especially as I’d disabled most of XP’s bells and whistles to make it run like Windows 2000. Essentially, I’ve been using the same operating system for an entire decade, and now I’ve been forced to change some long-held habits!

All of which leads me on in a fairly rambling way to what I had originally intended to talk about at the start of 2010 – whether we’re now living in a new decade. The media seem pretty convinced that we’ve abandoned the “Noughties” in favour of the “Teens”, but the maths says otherwise – it won’t be until the end of 2010 and the start of 2011 that we enter the next decade.

It’s the same argument that you probably tired of in the years leading up to December 31st, 1999. At the time, mathematicians said that millennial celebrations should be put off until the start of 2001, while the rest of the world largely ignored them.

Simply put, our calendar system starts at the year 1 AD, not the year 0 AD. One year later is 2 AD, ten years later is 11 AD, and two-thousand years later is 2001 AD. So, new decades start with years ending in a “1″.

But when we speak of the Noughties, we obviously mean the years 2000 to 2009. The year 2010 can’t be a Noughtie, because it doesn’t have a 0 in the right place. And hang on a moment, isn’t the calendar based off the life of Jesus, a man whose date of birth we know very little about? And lets not even start on the missing 11 days of September 1752.

Given the human desire for patterns and our fondness of round numbers, it’s probably best if we stick to celebrating 2010 as the new decade – it’s no less arbitrary than any other choice. Even so, I can’t help wanting to go with 2011. It may be ugly, but it’s mathematically correct!


  1. 2 Comments

  2. The situation becomes much easier if you point out to someone who quibbles about which year ends a decade that ‘decade’ can, technically, refer to any 10-year span. As a result, you can declare the end of the decade any time you like, and if pressed, simply say ‘the decade which started 10 years ago’!

    By David on Wednesday 13 January, 2010 at 9:24 am

  3. Well, if you’re on Jeopardy, you’ll need Alex Trebec’s rather artificial definitions of century and decade.
    A decade is a period of ten years, and a century is 100 years. Those are the definitions in my Webster’s. Therefore, 1975-1984 is a decade.
    If you specify “the ’70′s” that defines the decade with “70″ in the year numbers. Therefore 1970-79. The year 1980 was no more part of the seventies than 100 is a two-digit number.

    By feralboy12 on Sunday 31 January, 2010 at 11:32 pm

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