I wasn't really going to get into this one for a couple of years but Roland (10,000 BC, Godzilla, Independence Day) Emmerich has bumped it up my schedule. Next month sees the release of the 2012 movie, the premise of which is that the world will end in a massive catastrophic event on the 21st of December 2012. This is all said to have been predicted in the "long count" calendar system of the first millennium meso-american civilisation, the Maya.

Oh god, where to start...

Emmerich has a penchant for mashing up history (and geography for that matter; 10,000 BC had mammoths charging around the pyramids) so I dread to think what he's done with the Mayan calendar. Don't get me wrong, I think it'll be great entertainment - I remember the Long Now Foundation had a big night out to go see 10,000 BC - but it'll do nothing to contextualise history.

Without wishing to alarm anyone, the problem with debunking this one is that there are elements of truth in it. Wrap these in a few layers of new age catastrophism, add some special effects and you have a Hollywood blockbuster. And much like The Da Vinci Code you know it's hokum but differentiating the fact from the fiction requires digging through some rather arcane material.

I don't claim to be an expert on the Maya but I have visited many of the great Mayan sites in Mexico and I know enough about astronomy and ancient calendar systems to throw my [tinfoil] hat in the ring, so here goes...

The Fact: The Maya kept count of many cycles of differing length. The longest cycle, the "Long Count" will reach the end of the 13th Baktun on the 21st December 2012 (Gregorian). In long count notation this looks like .

Everything else is speculation. Notice I didn't say this will mark the end of the Long Count, never mind the world. Some scholars argue for a cycle length of 20 Baktun ending in The Mayans were undoubtedly excellent astronomers and they were fascinated by cycles, but cycles don't end, they just start round again. The world isn't going to end - this is a rollover problem. For an astronomical perspective on the issue you might like to read Gia Milinovich's article on the subject or a series from Universe Today.

If you are a proponent of catastrophism then you're not alone either. In the bunker you'll find former MI5 agent and erstwhile Messiah of Surrey, David Shayler. The movie viral is in full swing now so if you like your theories half-baked then you can follow Charlie Frost at thisistheend.com and on Twitter. And if you're still on the fence then I'd suggest waiting until the 22nd to buy your Christmas presents.