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Our calendar is central to our religion, honored travler; central to our very lives. First of all, we observe two separate calendars, a solar calendar of 365 days (adjusted in leap years), and a Sacred Calendar, known as the Tonalpohualli, which consists of 260 days. Let me begin telling you about these by explaining that each day is defined by a sign and a number; the numbers are one through thirteen, and the signs are listed below, showing the way a series of 21 days beginning with the number one and the sign Cipactli would be named:
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...and so on. Since there are 20 signs and 13 numbers, any given day sequence will repeat
every 13x20=260 days, thus the 260-day Sacred Calendar.
You might have noticed that only four of the signs, Calli, Tochtli, Acatl, and Tecpatl, can be the names of a year - a Solar Year. This is because a year is named for the first day in that year, and, since there is one Sacred Year + 105 days in a Solar Year, the sign of the first day will advance by 5 every year, meaning that only 20/5=4 of the day-signs can be year-names. The numbers are not evenly divisible, so any number can define a year.
The Solar Year is divided into eighteen months, each one twenty days long. Since there are
twenty signs, each month of a given year begins on the same sign as the year. 18x20=360, which means 5 (or 6) days are left over to finish the year; these are known as the Nemotemi, the "Five Useless Days." I will be happy to speak of these eighteen months, and of the ceremonies and rituals that mark them, if you desire...
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Now, just a little more arithmetic shows that, since only four of the signs can define a year
but since all thirteen of the numbers can, the cycle you see moving above begins to repeat
itself after 13x4=52 years, a "Bundle of years." Such a bundle is defined as beginning in a
year whose first day is Ome Acatl (Two Reed), which is why the number two, along with the
year-signs Acatl, Tecpatl, Calli, and Tochtli, are shown in red in the moving graphic. Fifty-
two years is also the amount of time it takes for Venus to make one complete cycle of its
phases and positions relative to the earth and sun.
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