It's the end of the world as we know it

Apparently the world is coming to an end on December 21, 2012.

Say What?

I wonder why they don't just make it December 12, 2012 -- that way it would be written as 12/12/12. Why would that be the end of the world? I dunno. Why 9/9/1999? (Was that one of the dates the world is suppose to come to an end?) Why 12/31/1999? :D