What we call the Mayan calendar is actually a set of three interlocking calendars, the sacred calendar of 260 days called the Tzolkin, the solar calendar of 365 days known as the Haab, and a Long Count calendar of much longer time periods. When the Mayans inscribed a date on a temple wall or a stone monument, they wrote the date using all three calendar notations. Every 52 years, the Tzolkin and the Haab come back in sync with each other. This was called a Calendar Round.
The Tzolkin or sacred calendar consisted of 20 periods each with 13 days for a 260-day count. Each day had a number and a name, the numbers from 1 to 13 and 20 day names. When the 13 numbers were gone through, they began again, and the 20 day names continued. When the day names were gone through, they repeated, and the numbers continued up to 13. The cycles of 13 and 20 repeated until they came back to the first number, first name again in 260 days. The priests who kept the calendars used the Tzolkin to determine days for sowing and harvest, military triumphs, religious ceremonies and divination.
The solar calendar or Haab has 365 days made up of 18 months of 20 days each, which adds up to 360 days. The remaining five days at the end of the year is an unlucky, dangerous time known as the Wayeb. Mayans stayed home and neglected all activities during this time to avoid disaster. In the Haab calendar, a day is represented by a number in the month, then the name of the month. There were 19 month names, plus Wayeb for the dreaded five-day month, making 20 month names.
Long Count Calendar
In order to keep track of longer periods of time, the Mayans used the Long Count calendar. The Long Count counts all the days since the beginning, which the Mayans marked as August 11, 3114 B.C. The Long Count calendar is cyclical as each period of time will begin again, but it is also linear. Because it is linear, it can take into account dates far in the future or in the past. The basic unit of this calendar is the tun, a year of 360 days, the basic Haab year without the five-day Wayeb. Long Count dates are expressed in five digits. The five digits represent a kin (day), uinal (month), tun (year), katun (20 years) and baktun (20 katuns).
Most Mayan dates note both the day of the Tolzkin and the Haab calendar. For instance, a day may be marked as 2 Chik’chan 5 Pop, with 2 Chik’chan being the date in the Tzolkin calendar and 5 Pop the date in the Haab, being the 5th day of the month Pop. The next day would be 3 Kimi 6 Pop. When the Mayans inscribed a date on a stela, however, they also included the five digits of the Long Count calendar. Thus January 1, 2000 would be written 188.8.131.52.2 11Ik 10 K’ank.