Well I'm not sure about the Mayan calendar, but I do know about the Christian Bible and what is said in revelations.
They say the Anti-Christ will come as a very smooth man, with an answer to all a nation's problems, there will be two good years, followed by two bad. (For the hell of it lets say its Obama, four years from now it would be 2012.)
People would worship him, and little by little would surrender everything to him. Everyone would love the beast, and eventually there would be one huge system that governs everything. Starting with currency. (Lets just say something similar to the European Union, but on a global scale. This could fix a lot of the economy issues and earn the beast a lot of supporters left in awe)
The bad two years would be persecution of any who disagreed with him, tortures and such, imprisonment, followed by beheading. Christians (and all people with religion I presume, along with any who doubt the sovereign nature of the leader) would be attacked.
That time is called the Tribulation, they say the mark of the beast could be UPC. In Revelations it is stated that people cannot even purchase food and supplies without that Mark (most places will not sell an item without a UPC).
End of days is supposed to happen somewhere in that year. Last people to make it to heaven are those that refused the Mark through torture and all that. In the end everyone in hell and Earth is thrown into a big abyss.
Of course, we'd have to count on the Mayans being right on their calendar, and Obama being the anti-christ for this all to happen.
I personally think 2012 will just be another year

.