In the accompanying table, each of the signs, called tonallyby the Aztecs, rules
a single day in the order, from left to right. After 20 days the cycle begins again. Along
with these 20 signs run 13 numbers as follows: (1) Crocodile, (2) Wind, (3) House,
(4) Lizard, (5) Serpent, etc., to (13) Reed. After that comes (1) Ocelot, (2) Eagle, (3)
Vulture, etc. It turns out that there are 20 cycles of the 13 numbers in exactly the
same number of days as 13 cycles of the 20 signs. This full cycle is one of 260 days and
is called the 260-day astrological calendar; the tzolkinof the Maya and the tonalpouhal-
liof the Aztecs. Each sign rules a day and is called a day-sign. The signs that are
attached to the number one rule the next 13 days and, since there are 20 of these in
the 260-day period, they operate like signs themselves, though in a different order
than the days. In other words, any given day in the cycle of 260 days is both a day-sign
and a part of a 13-day sign. These are only two of the fundamental building blocks of
Mesoamerican astrology, and they are a key to both the classification of individual
personality and the analysis of celestial events affecting society at large.Each of the 20 signs was said to be ruled by a specific deity. Correspondences
with the Aztec pantheon are known, but the Mayan correspondences have been lost
for the most part. Knowledge of the Aztec gods and goddesses is central to an under-
standing of the signs, just as an understanding of zodiac signs requires a knowledge of
planetary rulers. The few books of symbols and glyphs (called codices) that survived
the Spanish conquest reveal even other correspondences and hint at a complex body
of symbolic knowledge utilized by priests and astrologers when working with the
astrological system. From these books, eclipses and conjunctions could be predicted
along with the signs (blocks of time) in which they would occur. In the codices,
descriptions of the effects of the various combinations are stated alongside the rele-
vant mathematical detail.
Mesoamerican astrology is a complex subject and was not limited to the astrol-
ogy of individual personality and destiny. Astrologers practiced a kind of electional
astrology, evident from the dates chosen for coronations, wars, and treaties—dates on
which important planetary conjunctions or stations occurred. There was also a unique
mundane astrology that utilized blocks of time of 7,200 days, a period very close to the
length of the Jupiter/Saturn cycle, called a katun.The katun was regarded by the
Maya as the fundamental unit of time for political and cultural matters. Katuns were
grouped in bunches of 13 and 20, and 260 of them made up a creation epoch. Because
the Maya were excellent mathematicians and left behind many dates in stone, we are
fairly certain that the current epoch began August 11, 3114 B.C.E. and will end
December 21, 2112 C.E. The 5,125-year span of 260 katuns (called the Long Count by
archaeoastronomers or the Mayan calendar by the new age community) is almost
exactly one-fifth of a precession cycle. In Mesoamerican astrology, the passage of the
ages is not measured in twelfths of the precession cycle and indicated by signs (as in
age of Pisces, Aquarius, etc.); it is divided in fifths that are in turn divided the same
way as the 260-day astrological calendar, into 20 units of 13 and 13 units of 20. The
Harmonic Convergence of 1987 brought to the world’s attention the fact that we are
soon to enter the last katun (^1 ⁄ 260 th) of the entire creation epoch. According to most
researchers, this date was April 6, 1993. The Long Count is complete on December
21, 2012, and a new segment of the precession cycle then begins the following day.Mesoamerican Astrology
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