Why do most People think the world will end in "2012"?
There was a movie by that name that was released recently about a global disaster in 2012 that talks about the struggles of the survivors. That has led many to discuss this time frame and all the lore that surrounds it. I won't belabor a full accounting of the lore here, but if you're interested, you can look it up in Wikipedia.
I can tell you for certain that the world will not end in 2012. The Bible declares that there will be a taking away of the church to meet Christ in the air that will occur at some point in the future. Christians refer to this as the rapture, although this term is not used in the Bible itself. We don't know when this will happen, but it hasn't happened as of this posting.
Even if the rapture happens today, the world won't end in 2012. To be sure, there will be a great amount of destruction caused by the rapture of the church, particularly in the part of the world that is daylight where Christians will be actively going about their daily business. The greater the technical state of a particular country's civilization, the greater the damage is likely to be. Don't forget that many farmers and ranchers are Christian. There will be impacts in the food supply for those not raptured. The areas of the Earth which have higher percentages of real Christians may be impacted to a greater extent than other parts. The lesser and greater tribulation that follows will yield much more destruction. I haven't seen the movie 2012, but the outpouring of God's wrath on those left behind on the Earth after the church is raptured will probably put the movie's special effects team to shame.
The Left Behind series presents a fictional account of this period if you can't manage to wade through Revelation on your own. While it is fiction, the authors do a good job dissecting the prophecy of the tribulation period. My own notes on the tribulation period from a study of the books of Revelation and Daniel can be found in the section on Eschatology.
After the tribulation period, there is a millennial period that comprises 1,000 more years of history for the planet. So even after the tribulation, there is a long way to go before the actual end of the world.
The key thing is to always be ready for Christ's return so you don't have to worry about the tribulation or problems that might occur in the planet's future.
I know that the apostles were convinced Christ would return shortly. As far as I know, with the restoration of Israel as a country and the return of the Jewish people to that land, the last major Biblical prophecy that had to happen before the rapture occurred was completed. This process began at the United Nations in November 1947 and continued through to independence day May 14, 1948. Since then, the rapture could have happened at any time.
With the things that are happening today, I believe that the time for Christ's return for His church is relatively soon. Regardless, nobody knows how long they will live, so you need to make the decision to accept Christ as Savior and begin living the life He wants you to live now, while you have the chance. You might not make it to the rapture.