The tenth month of the Aztec
Xiuhpohualli (calendar) was Xocotlhuetzi, the Great Feast Day of the Day. The ancestors of the people were honored during this time. In comparison to the western calendar, the month covered the dates we know as August 12 through August 31.
The principal gods honored at this time were Yacatecuhtli, Xiuhtecutli and Xocotl. This time was celebrated by cutting down a large tree and bringing it to Tenochtitlan, where it would be decorated. Young boys competed to be the first and fastest to climb poles during the ceremonies.
The god Xiutecuhtli was specially venerated during this time period with fire ceremonies. The victims sacrificed to that god would be half roasted alive and then be killed by having their hearts removed.
Sources:
http://www.ancientmexico.com
http://www.crystalinks.com/aztecalendar.html
http://www.azteccalendar.com/introduction.html