The baktun is the largest of the commonly used units of the Maya Long Count, equal to twenty katuns, or 144,000 days, roughly 394 years. Long Count dates are conventionally written with the baktun first, as the leading of five numbers counting baktuns, katuns, tuns, winals, and kins since the mythic creation date, 4 Ajaw 8 Kumku, which corresponds in the standard correlation to a day in 3114 BCE. The completion of the thirteenth baktun from that point, in December 2012, drew wide popular attention and much misunderstanding; in the Maya reckoning it marked the turning of a great cycle, not an end of the world, and the count simply continued. Still larger units exist in some inscriptions. These are the features of the Maya Long Count, the linear day-tally carved on the monuments of the Classic period.
A Baktun is twenty Katun, 144,000 days, or roughly 394.3 solar years, the largest of the five standard places in the Long Count and the unit whose completion of its thirteenth cycle, 13.0.0.0.0, fell on 21 December 2012 in the widely used GMT (Goodman-Martinez-Thompson) correlation, which sets the Long Count's starting point 0.0.0.0.0 at Julian day number 584,283. That date attracted large-scale popular attention as a supposed end-of-the-world or global-transformation event, a reading epigraphers and Mayanists have consistently rejected: the Classic-period inscriptions that reference the 13th Baktun's completion, notably on Tortuguero Monument 6, describe it as an ordinary period-ending accompanied by the descent of a deity, in the same genre as other Katun and Baktun endings, and Long Count arithmetic continues without difficulty beyond it into a fourteenth Baktun and further, larger place values attested in a handful of inscriptions.