Here is an interesting video about the Mayan calendar.
Nasa says, " Just as the calendar you have on your kitchen wall does not cease to exist after December 31, the Mayan calendar does not cease to exist on December 21, 2012. This date is the end of the Mayan long-count period but then -- just as your calendar begins again on January 1 -- another long-count period begins for the Mayan calendar."http://www.nasa.gov/topics/earth/features/2012.html#mayans
Here is a link to the page where NASA answers questions about December 21, 2012.