baktun

A baktun is a unit of time in the Maya Long Count calendar. It represents a period of 20 katuns, for a total of 144,000 days. Because a tun is 360 days (18 uinal of 20 days), the system combines kin (1 day), uinal (20 days), tun (360 days), katun (7,200 days), and baktun (144,000 days) to form a hierarchical sequence.

In notation, a Long Count date is written as baktun.katun.tun.uinal.kin. For example, 13.0.0.0.0 marks 13 baktuns since the base date and is widely cited in discussions of the 2012 transition. A baktun is roughly 394 years long (144,000 days divided by about 365.24 days per year).

The Long Count is anchored to a base date, commonly associated with a GMT correlation constant of 584,283, linking Maya dates to the Gregorian calendar. By this convention, 13.0.0.0.0 corresponds to December 21, 2012. After that date, inscriptional counts may continue into the next baktun.

Baktuns are used to express long chronological spans in Maya inscriptions and scholarly work. The term is of Maya origin and denotes a substantial cycle in the Long Count. In some modern discussions, larger terms such as piktun, kalabtun, and exaktun—each representing 20 of the previous unit—appear, but these are less standardized and not part of the traditional, widely used Long Count. A commonly cited concept is the Great Cycle, often described as 13 baktuns, spanning about 5,125 years.