The Aztecs developed an intricate stone calendar to let them know when
to plant and harvest crops, as well as pray to the gods for the success
of the crops. The Aztec calendar had two different systems of keeping
track of time in their current world. They were called tonalpohualli and
The tonalpohualli was known as the "counting of the days."
It was 260 days long the time it took for the sun to cross
a certain point in the sky. Priests used this calendar to determine
the best days for activities such as sowing crops, building houses,
conducting specific ceremonies, inaugurating the new king and
going to war.
The xiuhpohualli was a civil, agricultural and ceremonial calendar
known as the "counting of the years." This calendar
was 365 days long.
While most cultures relied on the movement of the sun to recalibrate
their calendars, the Aztecs looked to the Pleiades instead because
that constellation passed directly over their community. The movement
of the Pleiades was their method of recalibrating their 365-day
calendar. This was necessary because each year is actually one
quarter of a day longer than 365
The Aztecs closely watched the movement of the Pleiades constellation
across the night sky. When the Pleiades disappeared, it marked
the sun's highest point in the sky and alerted the Aztecs to the
coming of the rainy season, which occurred near the end of April.
When the Pleiades again began to appear in the sky each night,
it marked the sun's lowest point and told the Aztecs that the
dry season (around November and December) was beginning.
A period called Xopan spanned the wettest period from June through
September (months 7 to 11). This period was symbolically associated
with the night, moon, Venus and the Pleiades.
The Aztec stone calendar recorded the history of all of these
world's as well as their own.
The Aztecs believed that four worlds had existed before theirs
and that each of these world's had been destroyed in some way.
In the first period, the world was destroyed by a great flood
and men were turned into fish. In the second, the world was destroyed
by violent winds and men were turned into monkeys. In the third,
the world was almost destroyed by fire. And in the fourth, the
world was almost eliminated by famine, or lack of food.
The Aztecs believed they were living in the fifth and last period,
which they called the Era of Movement. They believed that their
current world would someday be destroyed by a giant earthquake.
In addition, the calendar was used to let the Aztecs know when
to plant and when to harvest. Because the growth of food was so
important to the survival and success of the Aztec empire, the
Aztec gods were closely related to agriculture. The calendar also
let the Aztecs know when to celebrate and make sacrifices to the
gods to ensure the successful growth of crops.