Why do people say the world will end in the year 2012?

they said all the computers were going to crash in 2000 but nothing happened and they said everything was going to shut down but it never happened i am younger than 10yrs old im only a 9 yr old BUT it's still a tiny chace because of global warming and natural disaters and the ozone layer is very thin and its a hole in it nd the sun is coming closer towards earth