Answer: About 394 years

A baktun is made of 20 units of a measurement known as a katun, according to the Harvard-Smithsonian Center for Astrophysics. A baktun is the equivalent of 144,000 days.

Pictured is a sky caiman vomiting water on one of the last pages of the 12th-century Dresden Codex displayed at the Saxon State Library in Dresden, Germany. The document is also known as the "Codex Dresdensis." The Dresden Codex is one of four historic Mayan manuscripts that still exist in the world and that together suggest modern civilization will come to an end on Dec. 21.