|2||Wo'||black conjunction||11||Sak'||white storm|
|3||Sip||red conjunction||12||Keh||red storm|
|7||Yaxk'in'||new sun||16||Pax||planting time|
|19||Wayeb'||five unlucky days|
The Haab' comprises eighteen months of twenty days each, plus an additional period of five days ("nameless days") at the end of the year known as Wayeb' (or Uayeb in 16th-century orthography).
Bricker (1982) estimates that the Haab' was first used around 500 BCE with a starting point of the winter solstice.
The Haab' month names are most commonly referred to by their names in colonial-era Yucatec (Yukatek). In sequence, these (in the revised orthography) are as seen on the right: Each day in the Haab' calendar was identified by a day number within the month followed by the name of the month. Day numbers began with a glyph translated as the "seating of" a named month, which is usually regarded as day 0 of that month, although a minority treat it as day 20 of the month preceding the named month. In the latter case, the seating of Pop is day 5 of Wayeb'. For the majority, the first day of the year was Seating Pop. This was followed by 1 Pop, 2 Pop ... 19 Pop, Seating Wo, 1 Wo and so on.
Inscriptions on The Temple of the Cross at Palenque shows clearly that the Maya were aware of the true length of the year, even though they did not employ the use of leap days in their system of calculations generally. J. Eric Thompson wrote that the Maya knew of the drift between the Haab' and the solar year and that they made "calculations as to the rate at which the error accumulated, but these were merely noted as corrections they were not used to change the calendar."
The five nameless days at the end of the calendar, called Wayeb', were thought to be a dangerous time. Foster (2002) writes "During Wayeb, portals between the mortal realm and the Underworld dissolved. No boundaries prevented the ill-intending deities from causing disasters." To ward off these evil spirits, the Maya had customs and rituals they practiced during Wayeb'. For example, people avoided leaving their houses or washing or combing their hair.
- Kettunen and Helmke (2005), pp.47–48
- Zero Pop actually fell on the same day as the solstice on 12/27/−575, 12/27/−574, 12/27/−573, and 12/26/−572 (astronomical year numbering, Universal Time), if you don't account for the fact that the Maya region is in roughly time zone UT−6. See IMCCE seasons.
- Again, per Kettunen and Helmke (2005)
- p.121, J. Eric Thompson, Maya Hieroglyphic Writing. University of Oklahoma Press. (1971) ISBN 0-8061-0958-0
- Bricker, Victoria (1982). "The Origin of the Maya Solar Calendar". Current Anthropology. 23 (1): 101–103. doi:10.1086/202782.
- Coe, Michael D. (1992). Breaking the Maya Code. London: Thames and Hudson. ISBN 0-500-05061-9.
- Foster, Lynn V. (2002). Handbook to Life in the Ancient Mayan World. New York: Facts on File.
- Kettunen, Harri; Christophe Helmke (2005). Introduction to Maya Hieroglyphs: 10th European Maya Conference Workshop Handbook (pdf). Leiden: Wayeb and Leiden University. Retrieved 2006-06-08.