The peoples of Central America used a great number of calendar systems, but they all followed the same overall pattern. The calendar described here is the Mayan "Tikal" calendar.
The Tikal calendar used a cycle of 20 days with a name for each day in the cycle, and a cycle of 13 days with a cardinal number for each day in the cycle (starting with 1). These two cycles were counted concurrently, so that after day "6 Ik’" followed day "7 Ak’b’al" and then "8 K’an". A particular combination recurred after 260 days, which period was called the "Tzolk’in" in the Yucatecan language. The names of the days in the 20-day cycle were as follows: Imix’, Ik’, Ak’b’al, K’an, Chikchan, Kimi, Manik’, Lamat, Muluk, Ok, Chuwen, Eb’, B’en, Ix, Men, Kib’, Kab’an, Etz’nab’, Kawak, Ajaw.
There was also a year count, called Haab’, with a year of 365 days divided into 18 months of 20 days each and a 19th month with 5 days only. The months had names, and the days had numbers, and these were counted as we are used to today, so after day "1 Pop" followed day "2 Pop" and so on. However, the numbers started at 0 instead of 1. The Mayan names of the months were: Pop, Wo, Sip, Sotz’, Sek, Xul, Yaxk’in, Mol, Ch’en, Yax, Sac, Keh, Mak, K’ank’in, Muwan, Pax, K’ayab’, Kumk’u, Wayeb’. There were no leap years in the central American calendars, so the year count ran out of step with the seasons by about one day every four years.
a particular date was usually identified by its position in both the tzol kin and the haab, for instance as "6 Ik’ 2 Pop", and for the next day "7 Ak’b’al 3 Pop". After 52 years (of 365 days) the same tzol-kin/year-count designation would return. This period is often referred to as a "calendar round" or a "Mayan century".
In many cases, Mayan monuments display dates in only the calendar-round manner, which means that these dates return every 52 years (of 365 days). This means that we can pinpoint those dates in the modern calendar only up to a multiple of 52 years.
The Spanish conquistadores who conquered Central America in the 16th century ordered the destruction of much of the Mayan written records, and the precise correlation between the Mayan calendars and modern calendars is therefore not exactly known.
calendar function can return, in text form, the Tikal
designation (Tzolk’in – Haab’) for any date in the modern calendars,
based on the most widely accepted correlation between the Mayan and
For the third Mayan calendar, see Mayan Long Count.
Further reading: The Book of the Year: Middle American Calendrical Systems, by Munro. S. Edmonson; University of Utah Press, 1988.