Total hogwash.  But you never know..............

Nobody knows why Mayan calendar ends on the 21st Dec 2012.  Maybe they thought that's far enough date to chisel their stone calendars.  Maybe they think something catastropic will happen according to their astronomic knowledge.  Just because these primitive people limited their calendar to that date does not mean that the world will end then.

This much I know: there is no scientific evidence that anything will happen on that date.

Now there are nuts out there who believe that there is a planet just outside our solar system, a planet called Planet X or Nibiru or Eris.  They say that this planet is in a trajectory that will make it swing by Earth on 21st. Dec. 2012, which will cause the "polar shift", meaning south pole will become north and north pole will become south, which in turn will cause apocalyptic phenomenon that will eradicate most of humanity.   They even say that agencies such as NASA know about it and have been keeping it a secret.  I say "blah blah blah" to all those conspiracy theories.

It's up to you to join those nuts or not.  But I hope you are more rational than they are.