From; Wauchope, R. (1975) Handbook of Middle American Indians vol 14: Guide to Ethnohistorical Sources, part 3, Austin, T exas: Inioversity of Texas Press. Fig. 73 #2: after Valadés, Rhetorica cristiana, 1579.
And again, why were the calendars of the Maya re-created to read differently then the original researchers were able to determine, just by reading both the myths and texts that were available to them? Why would there have been such a "cover-up" of the data that, by the way, is still available to all? (See the above calender from 1579 or so.) The Veytia Chart is an excellent example of the native calendar even in 1579 and later scholars such as: Manuel Leon-Portilla, Jacques Soustelle, the Madrid Codex, have since confirmed such a calendar.
Since a 13-month year would only make a 260-day calendar, the actual number of months has to match Sahagún's number of months, i.e. 18 months, Yet, somewhere along the line, someone decided that the only calendar of worth was the 260-day calendar of the horoscopes.
Such calendar features were never useful to history nor have they been useful in any modern calendars, no matter how many rulers believed [or still believe] in the "luck of the [good] stars and the "evil portends" of the bad ones.
The 260-day horoscope calendar is the only other "numeration" that gives us any verification that the 13-week is also the four agricultural seasons, from burning the milpas, planting the maize, and the final harvest, with a whole extra season to celebrate a good harvest to be eaten, sold, or traded for necessities, and to thank their God for it.
The five extra days were added outside of the four quarters, even though they had to be taken into account after the years that produced no food. Yes, the skies had changed and the growing season also had to be accommodated to fit these odd days that had been added to the years.
The current concept of the calendar in Mexico proper is touted by those who learned the calendar from their parents and ancestors. Near El Tajin, the Voladores spin from their poles and the waiters and concessions nearby are equiped with some excellent information based on the ancient glyphic calendar system:
The four flyers, who are hand-picked to start their training at age 10, circle the pole 13 times each, he says, giving a total of 52 revolutions. The number 52, aside from being the number of weeks in a year, was important in Mesoamerican culture, which had two calendars -- the 365-day solar year and a 260-day ritual year. The calendars coincided every 52 solar years.……………" (See Flights of Fancy, JOURNEYS - THE SPIRIT OF DISCOVERY: BRENDAN SAINSBURY at Side Panel)Nevertheless, it was still necessary to retain the old calendar of the Maya (and the Aztecs, Mixtec, etc); otherwise, the glyphs and ancient histories in the Codices and on monuments can never be read properly. The horoscope has its place in the world, of course; but if the 13 are the number of weeks in a season, not the numbering of days, and the 52 revolutions are the current 365.25 number of weeks in a year, does one follow the 20 days per each of the 18 months that is found in the Codices, or are scholars to follow the information given out for the later centuries in Mesoamerica?
The ancient solar calendar, world wide, was originally 360 days, even in those codices. And, as above, in the VII century AD, the Copan Academy of Science changed the calendars to fit a 365-day year. Is that information to be destroyed by an overabundance of computer calculations that does not know to differentiate between the centuries of change? Even the Julian count does not accommodate the archaic calendar since it does not know when or how the calendar had to be altered to begin with.
So when was it decided that the original calendar had to be ousted? As far as I have been able to research the calendar, there is a new note in Jose Castillo-Torre (1955. 193) Por la Seňa de Hunab Ku in which he gives some very interesting data about the first day of the first month of the year 1583/4.