James Watt

There has been a bogus forward circulating Facebook and Twitter about the Mayan Calendar. It claims that the Mayans were unaware of our Leap Year system, therefore the world should have already ended. The forward going around reads:

There have been about 514 Leap Years since Caesar created it in 45BC. Without the extra day every 4 years, today would be July 28, 2013.

Also, the Mayan calendar did not account for leap year…. so technically the world should have ended 7 months ago.

While I appreciate the ultimate goal of this forward, whoever wrote it is very misinformed. The current era (known to the Mayans as a baktun) does end on December 21, 2012. However, the world will not end; the calendar simply rolls over to the next baktun. It’s very similar to the Gregorian date of January 1, 2000.

And just like we celebrated the beginning of the new millennium, the Mayans would have celebrated the beginning of a new baktun. This was not something to fear.

Julius Caesar did modify the Roman calendar in 45BCE to include Leap Years. This new calendar was called the Julian calendar. As of the time of posting, today’s date on the Julian calendar is only February 23, 2012. This is because the Julian calendar adds a leap year every four years, meaning that each year is 365.25 days long.

In reality, one solar year is ~365.24219878 days. In order to correct Caesar’s mistake, it was changed in 1582 to a calendar year equal to 365.2425 days. This was done by skipping leap years that were divisible by 100 unless they are also divisible by 400. For instance, the following years would have been leap years under the Julian calendar, but are now skipped: 1500, 1700, 1800, 1900. Likewise, the following leap years were not skipped because they were also divisible by 400: 1600, 2000. This system, known as the Gregorian calendar, is what we use today.

The Mayan calendar is very inaccurate when calculating years. Not only did they not account for leap years, they were completely wrong about how many days were in a year. The Mayan “tun” is 360 days long, equivalent of 0.986 years.

However, the date of December 21, 2012, is not based on Mayan tuns. It is based on the total accumulation of days since the beginning of the Mayan calendar. It is commonly accepted that the first date on the Mayan calendar is August 11, 3113 BCE on the Gregorian calendar. Therefore, we must start on that date and count forward in time.

The Mayan baktun is the equivalent of 400 Mayan tuns (years). But remember, their years are only 360 days long. 400 x 360 = 144,000. Therefore, each Mayan baktun is a total of 144,000 days long.

As of the time of posting, the Mayan date is 12.19.19.3.11. The first number represents the baktun, the second number katuns (20 Mayan years), the third number is tuns (Mayan years), the fourth is uinals (20 day “weeks”), and the final number is the day. I know that I’m making some history nut cringe at my over simplification of the Mayan calendar; I’m using “years” and “weeks” to make things easy to understand.

On December 21, 2012, the first number in the Mayan calendar will change from 12 to 13, making it 13.0.0.0.0. The last time this happened was on September 18, 1618, when the current baktun started. As you have already imagined, the Mayan date on that day was 12.0.0.0.0. Obviously, the world didn’t end.

But how do we know that 13.0.0.0.0 will happen on December 21, 2012? First, we need to calculate the total amount of days required to reach the 13th baktun: 144,000 x 13 = 1,872,000 days.

If we start counting from August 11, 3113 BCE, we probably won’t get very far. I don’t know about you, but counting to almost 2 million isn’t something that I have time to do. Instead, use any date calculator to do the math. Sure enough, you’ll always arrive at the same date: December 21, 2012.

Update 4/26/2012: I would like to clarify a misconception about when the Mayan calendar began. Some date calculators convert everything before Oct 15, 1582 to the Julian calendar. This is because dates recorded in history during that time were recorded on the Julian system. I didn’t see any reason to convert it twice so I used August 11, 3113 BCE on the Gregorian calendar and counted forward. However, the Mayan calendar began September 6, 3114 BCE on the Julian calendar. If your calculator is using the Julian calendar for older dates, please keep this in mind. For more information, please read the original message that prompted this.

Update 5/20/2012: Some people still disagree with the date calculator and/or simply do not understand this article. I posted a comment below, showing all of the work required to count days on the Gregorian calendar, further proving that the calendar does end on Dec 21.

Update 6/25/2012: Some small mix ups with the year because certain Gregorian calendars use the year zero while others do not. Please see this comment from a very informed reader who explains it all.

The Mayan Calendar The Aztec Sun Stone. Commonly, but incorrectly, shown to represent the Mayan calendar