I know why the Mayan calendar ran out on Dec 21 2012.
The guy carving it, was going round and round this rock tap tap tapping his chisel to make the long count calendar!
Just as he got to Dec 21 2012, and was about to start the next day the rock had a fracture in it and as he tapped it, that piece broke off and there was no room left on the rock to finish off the next few thousands of years!
So like all good stone carvers - he tossed that one out and went and got another bigger piece of rock and started again.... but you can bet after all that work even if he is dead now I bet he's still swearing and cursing!
Don'cha just hate it when that happens?