12/21/12 is just supposed to be end of the Mayan calendar. It's the common thought that the world will end, but that's not directly related to this date.
"The Hopi and Mayan elders do not prophesize that everything will come to an end. Rather, this is a time of transition from one World Age into another. The message they give concerns our making a choice of how we enter the future ahead. Our moving through with either resistance or acceptance will determine whether the transition will happen with cataclysmic changes or gradual peace and tranquility." - Joseph Robert Jochmans
I have no idea who this guy is but he summed it up mostly haha. It's simply the end of one era and the beginning of another. There is apparently going to be a significant change in the world, leading to possible destruction.
Think for yourself. Question authority.