<P> The 365 - day haab was produced by a cycle of eighteen named 20 - day winals, completed by the addition of a 5 - day period called the wayeb . The wayeb was considered to be a dangerous time, when the barriers between the mortal and supernatural realms were broken, allowing malignant deities to cross over and interfere in human concerns . In a similar way to the tz'olkin, the named winal would be prefixed by a number (from 0 to 19), in the case of the shorter wayeb period, the prefix numbers ran 0 to 4 . Since each day in the tz'olkin had a name and number (e.g. 8 Ajaw), this would interlock with the haab, producing an additional number and name, to give any day a more complete designation, for example 8 Ajaw 13 Keh . Such a day name could only recur once every 52 years, and this period is referred to by Mayanists as the Calendar Round . In most Mesoamerican cultures, the Calendar Round was the largest unit for measuring time . </P> <P> As with any non-repeating calendar, the Maya measured time from a fixed start point . The Maya set the beginning of their calendar as the end of a previous cycle of bak'tuns, equivalent to a day in 3114 BC . This was believed by the Maya to be the day of the creation of the world in its current form . The Maya used the Long Count Calendar to fix any given day of the Calendar Round within their current great Piktun cycle consisting of either 20 bak'tuns . There was some variation in the calendar, specifically texts in Palenque demonstrate that the piktun cycle that ended in 3114 BC had only 13 bak'tuns, and other inscriptions seem to have used an exceptional cycle of 13 + 20 bak'tun in the current piktun . Additionally, there may have been some regional variation in how these exceptional cycles were managed . </P> <P> A full long count date consisted of an introductory glyph followed by five glyphs counting off the number of bak'tuns, kat'uns, tuns, winals, and k'ins since the start of the current creation . This would be followed by the tz'olkin portion of the Calendar Round date, and after a number of intervening glyphs, the Long Count date would end with the Haab portion of the Calendar Round date . </P> <P> Although the Calendar Round is still in use today, the Maya started using an abbreviated Short Count during the Late Classic period . The Short Count is a count of 13 k'atuns . For this reason, there is no direct correlation between the Long Count and the European calendar . The most generally accepted correlation is the Goodman - Martínez - Thompson, or GMT, correlation . This equates the Long Count date 11.16. 0.0. 0 13 Ajaw 8 Xul with the Gregorian date of 12 November 1539 . Epigraphers Simon Martin and Nikolai Grube argue for a two - day shift from the standard GMT correlation . The Spinden Correlation would shift the Long Count dates back by 260 years; it also accords with the documentary evidence, and is better suited to the archaeology of the Yucatán Peninsula, but presents problems with the rest of the Maya region . The George Vaillant Correlation would shift all Maya dates 260 years later, and would greatly shorten the Postclassic period . Radiocarbon dating of dated wooden lintels at Tikal supports the GMT correlation . </P>

When did the maya classic age occur and what defined it