Long Count
A brief explanation of the The Maya "Long Count" calendar

The Maya had two major calendars running simultaneously: A 365-day solar calendar called the Haab' which had eighteen "months" of twenty days each, plus an additional period of five days ("nameless days") at the end of the year, and a 260-day ceremonial calendar called the Tzolk'in which had 20 periods of 13 days.

Because the two calendars were based on 365 days and 260 days respectively, the whole cycle would repeat itself every 52 Haab' years exactly. This period is generally known as the Calendar Round.

The Haab' and the Tzolk'in calendars identified and named the days, but not the years. The combination of a Haab' date and a Tzolk'in date was enough to identify a specific date to most people's satisfaction, as such a combination did not occur again for another 52 years, above general life expectancy.

To measure dates over periods longer than 52 years, the Mesoamericans devised the Long Count calendar.

The Long Count calendar identifies a date by counting the number of days from August 11, 3114 BCE. Maya writing consisted of a highly elaborate set of glyphs, which were laboriously painted on ceramics, walls or bark-paper codices, carved in wood or stone, or molded in stucco. The calendar system used particular glyphs, for which we substitute numbers separated by periods. Each number represents an interval, with the smallest interval on the right, increasing as you move to the left. From right to left, the intervals are named K'in, Winal, Tun, K'atun, and B'ak'tun. Rather than using a base-10 scheme, like Western numbering, the Long Count days were tallied in a base-20 scheme. Thus is equal to 25, and is equal to 40.

The Long Count is not consistently base-20, however, since the second digit rolls over to zero when it reaches 18. Thus does not represent 400 days, but rather only 360 days.

The following table shows the period equivalents as well as Maya names for these periods:

Representation Long Count subdivisions Days Approx. solar years 1 K'in 1 1/365 1 Winal = 20 K'in 20 1/18 1 Tun = 18 Winal 360 1 1 K'atun = 20 Tun 7,200 19.7 1 B'ak'tun = 20 K'atun 144,000 394
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