The fourth month of the Aztec Xiuhpohualli (calendar) was Uey Tocoztli. In comparison to the western calendar, the month covered the dates we know as April 14 through May 3.

This month was known as "The Great Vigil" and the chief gods honored and worshipped during this time were Centeotl, Chicomecoatl and Tlaloc. Children were ritually sacrificed to the gods on Mt. Tlaloc and at Pantitlan in Lake Tezcoco in order to ensure good weather for growing crops.

The virgins of Tenochtitlan would lead a procession through the city while carrying seven ears of corn and a blessing of the sacred seed corn would take place. Dried seed corn consecrated by Chicomecoatl priestesses were thrown to the crowds. The people gathered as many as they could and saved the seeds for the next planting season.