 This took place at the end of each cycle of the Aztec calendar round (every 52 years), when the gods were thought to be able to end their covenant with humanity.Feasts were held in honor of Xiuhtecuhtli to keep his favors, and human sacrifices were burned after removing their heart.The annual festival of Xiuhtecuhtli was celebrated in "Izcalli", the 18th veintena of the year.