Historically, the Aztec name for the huge basaltic monolith is Cuauhxicalli Eagle Bowl, but it is universally known as the Aztec Calendar or Sun Stone. It was during the reign of the 6th Aztec monarch in 1479 that this stone was carved and dedicated to the principal Aztec deity: the sun. The stone has both mythological and astronomical significance. It weighs almost 25 tons, has a diameter of just under 12 feet, and a thickness of 3 feet.
The stone is now displayed in the Museo National de Antropología in Mexico City. The sign there in June 2007 said that the Stone of the Sun was incorrectly identified as the Aztec Calendar because of the symbolic content with names of the days and cosmogonic suns. In fact, reports the Museo, this stone was a large gladiatorial sacrificial altar (temalacatl).
Many religions were based on the cult of a sun god, including ancient Egyptian religion, Japanese Shinto, and the Inca religion. The Inca rulers believed they were descended from Inti, the sun god, and worshipping him was a state-imposed cult. He was usually portrayed as a human face within a sun disk. He lives on in the names of many Andean organizations, and in tourism, but above all in Inti Raymi, the annual festival of the winter solstice, held in Cuzco on 24 June, according to the Inca calendar. Inti Raymi marks the beginning of the sun’s new year, and is therefore a reason for celebration.
Excerpted from: Aztec Calendar - Sun Stone and Inti, the Inca sun god