Author’s note: I will be putting on pictures of the glyphs soon.
The word Haab (or “vague year”), is the modern name for the ancient Maya’s sun-based calendar used for knowing when to plant crops. This calendar is made of 20 “months” (uinals) of 18 days (18 times 20 is 360), plus a group -- or “month”-- of 5 days at the end of the year. Altogether, this makes the Haab a 365-day calendar.
Months are referred to by their names in Yucatec Mayan: Pop, Uo, Zip, Zotz’, Zec, Xul, Yaxkin, Mol, Ch’en, Yax, Zac, Ceh, Mac, Kankin, Muan, Pax, Kayab, Cumku and finally Uayeb -- the 5 day period whose name may mean “resting of the year”. Each month was ruled by a deity who was its patron.
How The Haab Worked
Unlike our calendar, instead of each month being numbered 1 through 30, 1 through 31 or 1 through 28 (or 29), the days of each Haab month were numbered 0 through 19. For example, the days of month of Uo would be written 0 Uo, 1 Uo, 2 Uo and so on through 19 Uo -- and then the next month would begin (0 Zip). The same process was used for Uayeb, in that the 5 days were numbered 0 through 4.
The first day of a month could be referred to as the “seating” of the month -- so, for example, 0 Cumku is the “seating” of Cumku. The particular influence of a month began on this day of “seating”. This also means that although 0 Pop was the beginning of Pop -- the first month of the Haab -- 1 Pop was still the Haab’s new year’s day.
Uayeb had a special consideration to the ancient Maya. It was considered an unlucky period of days.
As is known, the year is actually about one-quarter of a day (6 hours) longer than 365 days. People working in the Maya field of archaeology have found that some ancient Maya seem to know this fact, though no one seemed to have adjusted the Haab to express this.
“A Forest of Kings; Linda Schele, David Friedel; 1990
“The Ancient Maya”; Robert J. Sharer, Loa P. Traxler; 2006