As a Catholic, we're taught that we never know when the World will end. Now, you're obviously not Catholic, however there is something YOU can learn from this mindset.
Nobody knows whether or not there is a God, there is no way to prove that there is a God or not through science.. Same goes for doomsday prophecies, there is no way to prove that it'll happen on this day in this year. Anyone who can claim otherwise is lying or needs to be in a mental hospital.
As far as I'm concerned, May 21st 2011 is just another day in the office. No need to circle it on the calendar.