Actually, they never even CALLED it the end of the world (modern-day survivors of the Mayan culture are annoyed as hell about that artificial meaning applied to it).
Yup, the Mayan calender in question (they had several) is calender on a 5,100 year cycle based off of their astronomical observations. All this means is that on 12-21-12 there will be some sort of astronomical alignment which was important to the Mayans, and the calender will start over. For the Mayans it means the beginning of a new age. It holds no real importance to anyone else unless perhaps you are a practicer/believer of astrology.
It's really just a calender rolling over. Do we predict doomsday every Dec. 31st when our Julian calender rolls over?... Of course not. But somehow because this calender is a much, much longer cycle a few whackos have predicted doomsday when it rolls over. People have been predicting the end of the world as we know it for thousands of years, someday one of them may be right, but it will be pure luck.