It doesn't really matter that Mayan's didn't account for leap years. Their calendar works a bit differently. Regardless, they didn't predict the end of the world either, idiots did that a whole lot later. For Mayans this date is more about the beginning of the new age, and a start of a new calendar. Much like when the calendar in your kitchen or whatever ending on January 31st doesn't mean the end of the world, neither does the end of a Mayan calendar. People need to relax.
I don't understand this fascination with THE END and such and so forth. The only thing it makes me think about is how if anything at all were to happen in the universe, how insignificant we all really are. Even the most important people on this planet are nothing in the grand universal scheme of things. And if a great cosmic event were to actually happen (also worth being stated that a few of our scientists with modern technology would be able to predict it to begin with same way as any ancient civilization) there is fuck all we can do about it.