The Mayan Calendar ends on December 21st, 2012 but does that mean something may happen on that day in my opinion it could but then again nothing may happen. For me I don't find this doom and gloom end of the world stuff fasnicating not by a long shot.
Here's the wiki entry about it
End of the world?
The end of the 13th baktun is conjectured to have been of great significance to the Maya, but does not mark the end of the world. According to the Popol Vuh, a sacred book of the Maya, we are living in the fourth world. The Popol Vuh describes the first three creations that the gods failed in making and the creation of the successful fourth world where men were placed. The Maya believed that the fourth world would end in catastrophe and the fifth and final world would be created that would signal the end of mankind.
The last creation ended on a long count of 126.96.36.199.0. Another 188.8.131.52.0 will occur on December 21, 2012, and it has been discussed in many New Age articles and books that this will be the end of this creation or something else entirely. However, the Maya abbreviated their long counts to just the last five vigesimal places. There were an infinitely larger number of units that were usually not shown. When the larger units were shown (notably on a monument from Coba), the end of the last creation is expressed as 184.108.40.206.220.127.116.11.18.104.22.168.22.214.171.124.126.96.36.199.0.0.0.0, where the units are obviously supposed to be 13s in all larger places. In this age we are only approaching 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.188.8.131.52.0, and the larger places are nowhere near the 13s that would match the end of the last creation. (Schele and Friedel 1990: 430)
This is confirmed by a date from Palenque, which projects forward in time to 184.108.40.206.0.0, which will occur on 13 October, 4772. The Classic Period Maya obviously did not believe that the end of this age would occur in 2012. According to the Maya, there will be a baktun ending in 2012, a significant event being the end of a 13th 400 year period, but not the end of the world.