Answer: Calendar
Explanation:
Basically, the Mayan Calendar was going through cycles, and December 21 2012 was the end of a cycle. It was close to the 13th Bak’tun, but instead of moving towards the next Bak’tun and so on, the Mayan calendar actually reset itself back to 0. But the Mayans did not predict the end of the world, we decided to interpret the calendar that way.