There has been a lot of silliness about the Mayan calendar lately. Supposedly it ends today, and some people thought that would (magically) cause the world to end with it. Just like all the other times the world has ended, right?
I have a nifty application on my telephone. It is called MayanTime, and it’s from SwampBits. It tells me that today is 184.108.40.206.0, and it explains the units of the calendar. That “13” is the Baktun, each of which lasts 144,000 days.