Did you ever have a spirograph? The toy had different plastic wheels that meshed with one another and revolved like a clock mechanism. You had to insert a pen and move it round the wheel to create a series of increasingly complicated circular designs on a sheet of paper beneath. The Mayan calendar worked in a similar way.
The first cycle in the Mayan calendar had 13 numerals and the second wheel had 20 named days. The two wheels revolved like a cogged mechanism, so it would be 260 days before the same point was reached again as the two circles rotated. This was then meshed with a third wheel of 365 days (known as the ‘vague year’), but of 18 months instead of our 12. Each month lasted 20 days with a ‘filler’ month of five days.
The Mayans appear not to have worried about the extra quarter day (that’s why it was a ‘vague year’). We do allow for this and that is why every four years we have a leap year (2012 is one), in
order to keep our calendar in sync with the movement of the Earth around the Sun.
The Mayan cycles would give a calendar of 18,980 days, or 52 years. For longer time spans there was the ‘long count’ with a unit of measurement called the bak’tun of 144,000 days. 13 of these bak’tun have passed since the cycle started in 3114 BCE and it ends later this year on 23 December – 1,872,000 days later!
People have speculated the end of this period of time will be marked by a terrible cataclysm that will wipe out the human race. As the Mayan calendar projects dates of anniversaries well into the future (long after 2012), I for one intend to sit back, not do anything rash and see what happens.
Answered by Bryan Sitch, Manchester Museum.