The Long Count Calendar

Topical Press Agency/Getty Images A Mayan calendar column was found in Quirigua, Yucatan peninsula, Mexico, on August 13, 1929.

Unfortunately, the Long Count calendar isn't as simple as combining two calendars together to get new dates. It's a little more complicated and abstract. In order to understand the Long Count, you first need to become familiar with a few terms:

• One day - kin
• 20 days - uinal
• 360 days - tun
• 7,200 days - katun
• 144,000 days - baktun

The span of the Long Count calendar is called the Great Cycle, and lasts approximately 5,125.36 years [source: Jenkins]. To find the Long Count date that corresponds with any Gregorian date, you'll need to count the days from the beginning of the last Great Cycle. But determining when the last cycle began and matching that up to a Gregorian date is quite a feat. English anthropologist Sir Eric Thompson set out to determine the date, and he looked to the Spanish Inquisition for help.

What transpired was known as the Thompson Correlation. Events that occurred during the Inquisition were recorded on both the Mayan Long Count calendar and the Gregorian calendar. Scholars then gathered dates that matched on both calendars and compared them to the Dresden Codex, one of four Mayan documents that survived the Inquisition. This codex confirmed the date long thought by Thompson to be the beginning of the current Great Cycle -- August 13, 3114 B.C. [source: Mayan Long Count].

Now that we have the beginning date of the Great Cycle, let's put the Long Count into practice. We'll take a date that's familiar to many Americans -- July 20, 1969, the day Apollo 11 landed on the moon. In the Long Count calendar, this date is written as 12.17.15.17.0 . You'll notice there are five number places in the date. Reading from left to right, the first place signifies the number of baktuns since the beginning of the Great Cycle. In this case, there have been 12 baktuns, or 1,728,000 days (144,000 x 12) since August 13, 3114. The second place relates to the number of katuns that have taken place. Then it continues on to the right with the number of tuns, uinals and kins. If you would like to see more Gregorian conversions, you can download a conversion calculator here.

The Mayan Pyramid Built around 1050 in Chichen Itza, Yucatan, Mexico, the Mayan Pyramid was a physical calendar. Each of the four sides of the pyramid has a staircase, each with 91 steps and a platform. Adding all four sides together, there are a total of 365 steps. The dates inscribed into the Mayan pyramids all were written in the Long Count format. Roberto Vannucci/Dreamstime.com The Mayan pyramid in Chichen Itza. ­­

For more information on the Mayan calendar and culture, and related topics, continue to the next page.