Some day the world as we know it will come to an end, when Jesus Christ returns in glory to destroy all evil and set up His kingdom of perfect peace and justice. And the Bible warns us to be ready for that day.
But the Bible also tells us that no one knows exactly when this will happen, because God hasn't revealed it to us (see Mark 13:32). In fact, it tells us that Christ's coming will be like that of a thief who comes when everyone is asleep -- unexpectedly and suddenly. The Bible says, "For you know very well that the day of the Lord will come like a thief in the night" (1 Thessalonians 5:2).
This is why you shouldn't take seriously any supposed "prophecy" claiming the end of the world will occur on a certain date. Some of these come from people who sincerely believe the Bible and want to learn from it -- but others (such as the "prophecy" you mention about the end of the world coming in 2012) come from pagan sources. Either way, you shouldn't let them make you fearful.
The real question, however, is this: Are you ready to meet God? God loves you, and the most important decision you will ever make is your decision to follow Jesus. Not only will He take away your fears, but He'll be with you and guide you every day as you open your life to Him. Ask Him to come into your heart today.