Each baktun represents 144,000 days — or nearly 400 years. The 13th (and, some say, final) baktun of the Mayan calendar is slated to come to an end on the solstice marked on Dec. 21, 2012.

“It’s a big deal — if you’re an ancient Maya astronomer priest,” Stuart says. “But apart from that, they didn’t say anything about … what will be happening.”

Stuart and other researchers have compared what’s about to happen to the Mayan calendar to an odometer on a well-driven car: The years will simply click over. If the car’s odometer runs past its complement of numbers, you can still drive it.