The world will not end. Stop buying into the hysteria of the silly masses.
Putin was right: the world will truly end when the Sun goes nova. That's 4.5 billion years from now. We will all die, unless we escape by intergalactic space travel.
21 Dec 2012 on the Gregorian calendar (forced onto us by the Catholic Church) is the end of a Mayan Long Count calendar (there are three main calendars, each for different purpose) cycle. A cycle that lasted for thousands of years.
http://www.kmov.com/home/How-the-Mayan-calendar-actually-works-184294431.html
http://www.timeanddate.com/calendar/mayan.html
The Gregorian calendar is quite inaccurate as the Earth orbits around the Sun in 365.25 days. The Gregorian calendar has to make up for this inaccuracy by having a leap year (366 days) every 4 years. Think about it: suppose you were to live on another planet, say Mars. Mars takes 687 days to orbit around the Sun. How are you going to use the Gregorian calendar there?
In fact, the Chinese and Islamic lunar calendars are much more useful than the Gregorian calendar, as they follow the moon cycles, and you can predict quite accurately the seasons and the tides.