Mayan calendar

How it works

There is not a single “Mayan calendar” in the sense of one grid like January through December. Several counts share the same day and reset on different periods. A date in this system is a combination of those counts, the way a weekday plus a month-date plus a year number together name a Gregorian day. Drop one piece and the name is incomplete.

The two counts people meet first are the 260-day Tzolk’in and the 365-day Haab’. They tick every day. After 18,980 days they return to the same paired labels, because that span is 73 rounds of 260 and 52 rounds of 365. That combined cycle is the Calendar Round. It is long enough to name a day inside a lifetime without repeating the pair, and not long enough to number history by itself.

For spans longer than a lifetime, inscriptions use the Long Count: a tally of days from a conventional starting day, written in nested units. That tally does not care about month names. It cares that each unit rolls over after a fixed number of the unit below it.

None of these cycles is trying to be the Gregorian leap-year machine. The Haab’ is a 365-day year without a 29 February. Seasons therefore drift slowly against Haab’ dates if you watch across centuries. That is a property of a 365-day year, not a defect in the arithmetic.

The 260-day and 365-day counts

The Tzolk’in pairs 13 numbers with 20 day names. 13 times 20 is 260, so the pairings run through every combination before repeating. Each day advances both the number and the name. You do not get number 1 with the same name again until the whole 260-day round has finished.

The Haab’ is 18 named periods of 20 days, then a short period of 5 days, often called Wayeb’. 18 times 20 is 360, plus 5 is 365. The five leftover days are part of the year, not a gap in the calendar. They have a reputation in later commentary as an awkward close to the year; they still have dates.

Tzolk’in: 260 days, 13 numbers with 20 names. Haab’: 365 days, eighteen 20-day periods plus five extra days. Calendar Round: 18,980 days until both labels repeat together. Long Count: a day number from an origin, in nested units.

A full everyday name quotes both the Tzolk’in pair and the Haab’ position. Saying only “a 260-day calendar” is like saying the Gregorian system is only weekdays. The weekday is real. It is not the whole date.

The Long Count is a day number

Long Count units, in increasing size, are the kin (one day), the winal (20 kins), the tun (18 winals, so 360 days), the k’atun (20 tuns), and the bak’tun (20 k’atuns). The winal is the odd one: it rolls at 18, not at 20, so that a tun lands on 360 days, close to a Haab’ year. A bak’tun is 144,000 days.

When a bak’tun rolls over, later writers sometimes talk as if a world ends. The count itself does not stop. It behaves like an odometer. The widely discussed rollover associated with 21 December 2012 in the Gregorian calendar was the end of a bak’tun under a common correlation between the two systems. The Maya counts continued. Correlation is a scholarly mapping; different proposed constants shift the Gregorian equivalent, so a conversion is only as good as the constant you state.

A calendar with more than one wheel is not confused. It is refusing to let a weekday pretend it is a year. To place a Maya date on a modern wall calendar you need a correlation and you need all the pieces of the Maya name you are converting. A Tzolk’in label alone repeats every 260 days. It cannot pick a unique Gregorian year.