This topic makes me feel like an idiot every time it's brought up, only because I ever let it bother me.
Unless the Mayans were psychic enough to predict the rise of Caesar and the invention of the leap year, the day that their interpretations or calculations were created for went by July of last year.
The extra days completely threw off the cycle, and the day that would've otherwise stood as December 21'st, 2012 is gone.
That being said, IF said Mayans WERE in some manner or another able to plan for the leap year (for all the astronomical prowess they were said to have had, it's not impossible to theorize they would've seen the extra change in the planet's rotation and counted it in), then it's going to make for a very interesting day.
I'm not worried about the end of the world.
I'm worried about the impending actions of the widespread crazies who ARE planning for it.