(Information taken from a book entitled Multicultural Mathematics Materials by Marina C. Krause and published by the
National Council of Teachers of Mathematics.) 

The calendar is evidence of the Aztec's knowledge of astronomy and mathematics. The calendar contained the pictographs for
their days, months and suns (cosmic cycles). The stone is 3.6 meters (12 feet) in diameter and weighs about 24 metric tons. It
took 52 years to complete, from 1427-1479, it is believed due to the use of only stone tools. This calendar is 103 years older
than the Gregorian calendar which is used worldwide today. 

Originally the Calendar Stone was placed atop the main temple in Tenochtitlan (pronounced tay-nohch-TEE-tlahn), the capital
of the Aztec empire. Today, Mexico City's cathedral stands on the site. The Aztec calendar faced south in a vertical position
and was painted a vibrant red, blue, yellow and white. The stone was buried by the Spaniards when they conquered
Tenochtitlan. The stone was lost for over 250 years until December of 1790 when it was found by accident during repair work
on the cathedral. Today it is located in the National Museum of Anthropology in Mexico City. 

The face of Tonatiuh is in the center circle of the stone. Around the face are four squares called Nahui- Ollin, or Four
Movement. According to Aztec legend, these squares represented the different ways that the four previous suns (or worlds)
had come to an end: first by wild animals, then by wind, by fire, and by floods. The Aztecs believed they were living in the fifth
and last world. 

Continuing outward, the next concentric circle shows twenty squares, each naming one of the twenty different days of the Aztec
month. Clockwise these days are as follows: 

Twenty Days of the Aztec Month 
     Snake - Coatl 
     Lizard - Cuetzpallin 
     House - Calli 
     Wind - Ehecatl 
     Crocodile - Cipactli 
     Flower - Xochitl 
     Rain - Quiahuitl 
     Flint - Tecpatl 
     Movement - Ollin 
     Vulture - Cozcacuauhtli 
     Eagle - Cuauhtle 
     Jaguar - Ocelotl 
     Cane - Acatl 
     Herb - Malinalli 
     Monkey - Ozomatli 
     Hairless Dog - Itzquintli 
     Water - Atl 
     Rabbit - Tochtli 
     Deer - Mazatl 
     Skull - Miquiztli 

The Aztec year consisted of eighteen months, each having 20 days. Each month was given a specific name. This arrangement
took care of 360 days (18x20), to which five dots were added inside the circle. These dots, known as Nemontemi, were
sacrificial days. 

The next concentric circle is composed of square sections with five dots in each section, probably representing weeks of five
days. Next are eight angles dividing the stone in eight parts. These represent the suns rays placed according to the cardinal
points. 

On the lower portion of the stone, two enormous snakes encircle the stone and face each other. Their bodies are divided into
sections containing the symbols for flames, elephant-like trunks, and jaguar-like forelegs. It is believed that these sections are
also records of fifty-two year cycles. A square is carved at the top of the calendar between the tails fo the snakes. Inside the
square the date 13 Acatl is carved. This corresponds to 1479, the year the calendar was finished. 

Eight equally spaced holes appear on the very edge of the calendar. The Aztec placed horizontal sticks here and the shadows
of the sticke would fall on the figures of the calendar; thus the stone also served as a sundial. 
(information recievced from http://riceinfo.rice.edu/armadillo/Schools/HSHP/aztec.html)

Religion
     Aztec religion was very different that that of modern religions.  The Aztecs believed in many gods, whom they paid tribute to every day of their lives.  The myth of creation was that Coatlique gave birth to the moon(Coylxauhqui), the stars, and the sun(Vitzilopochtl).
     Human sacrifices, as well as animal were a big part of Aztec religion.  They used sacrifice as a means of satisfying their gods when they believed that they were angry for some reason.  When an individual was sacrificed they would climb to the top of the pyramid(wearing a mask), stretch out over a convex stone, and then the priest would cut out the heart using a knife.  The number of sacrifices that were performed often depended on whether or not they were in a drought or not.  If the harvesting was good they did not sacrifice many people, however if there was a draught hundreds of people could be sacrificed.
     For warriors, the most honorable way to die was to be slain in battle or to volunteer to be sacrificed at an important ceremony.  At the less important sacrifices, prisoners were offered to the gods.  Before each of these ceremonies the participant was required to abstain from sex, and to eat only one unseasoned meal a day for four days leading up to the event.  These sacrifices played a continual role in the Aztec civilization, and were carried out until their demise. 
     It is estimated that over a quarter of a million people were sacrificed each year by the Aztecs.  This figure is roughly 1 percent of the population.  Anthropologist achieved this figure through a direct correlation with the number of temples that that have been found. 
Religion: more links.

Farming and Agriculture    
     The main activity in Aztec daily life was farming.  The people spent continuous hours cultivating the land, and because it was quite infertile to begin with they were always creating new methods to increase their yields.  The main methods that they used included irrigation, fertilization, and the building of terraces. 
     The principle crop of the Aztecs was corn, but they also grew such things as beans, peppers, avocados, and tomatoes.   Anthropologists have also determined that the farmers sometimes grew flowers, probably for the purpose of decoration.  The Aztecs did not have animals or plows to help them on the land, so farming was a laborious activity throughout their existence. 
     Upon harvesting their crops the Aztecs did a variety of different things to it. Sometimes they would grind the corn using a stone and a flat plat to make corn meal.  The corn meal was then used to make tortillas, which was the principle food of the lower and upper class. 

The Arts 
     The Aztecs exhibited many different styles of art, but the expression they favored most were sculptures.  Most of the sculptures were made out of limestone, which was and still is readily available in Mexico.  Most of the art they created was related to their religion.
     Designing clothes, mainly in the upper class was another form of art in the Aztec culture.  Women usually made the clothing, and they decorated them with beads, flowers and precious metals.  Gold was often used for decoration, and was abundant in the Aztec empire.  Gold, in fact was the main reason for Cortez to travel to Mexico in the first place.

Sciences 
     Most of the Aztec advances in science were in the area of astronomy.  Their most famous accomplishment was the building of a stone calendar, which took them 52 years to build.  The calendar itself was 3 feet thick, 12 feet in diameter, and weighed about 24 tons. 
     The Aztecs made scientific advances in the area of medicine as well.  Surprisingly the herbal medicines of the Aztecs were much greater than those of the Europeans during the same period.  The medicine was based on two areas, spiritual and herbal healing.  Many of the illnesses were blamed on the gods, thus spiritual healing consisted of prayer, and often animal sacrifice. 
     The Aztecs knew the power of the herbs, therefore they spent a great deal of time finding out what each one did, and what diseases they could be used to treat.  Over many generations they built up a wealth of knowledge, and in fact many of the remedies they first discovered are still being used today. 
 

The Conquest  
     In February 1519, Hernan Cortez was sent by the governor of Cuba, Diego Valesquez to explore the area occupied by the Aztecs.  For some reason at the last minute, Valesquez ordered Cortez not to go.  Disobeying his orders, Cortez set out with 400 soldiers, 100 sailors, and about 15 horses. 
     Cortez landed near Villa Rica de Vera Cruz, and upon his arrival he declared himself to be in supreme command.  Soon, Cortez and his men traveled inland, were they encountered the Tlaxcalan people who then surrendered.  After surrendering they joined forces with the Spaniards increasing the force to several thousand.
     When Cortez arrived, the Aztec emperor Moctezuma  the second greeted him with open arms, believing that he was the Aztec god Quetzacoatl, the god of civilization.  Cortez also received a woman translator, named Malinche, who is the mother of the first mestizo.
     When the Aztecs realized that he was not who they thought, the gave Cortez gold and jewelry in hope that this would get him to leave.  Instead the Spaniards became more greedy.  Cortez actually took Moctezuma the second as a hostage in order to receive a large ransom from the Aztecs.
     His actions soon caught up with him, and when Velasquez found out he sent forces to arrest Cortez.  Needing desperate help, Cortez asked for the help of Moctezuma.  However when he went out to speak to his people, the stoned him, until a few days later he died.    On June 30, 1520 Cortez fled the city, chased by Aztec warriors.  About 1 year later, a battle took place, leaving behind 40, 000  dead Indians, marking the end of the Aztec empire.
To read more about Aztec conquests click here

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