The first month of the
Aztec Xiuhpohualli (calendar) was
Atl Caualo. In comparison to the western calendar, the month covered the dates we know as February 13 through March 4.
This month was known as "The Ceasing of Waters" and the corn and rain gods were to be appeased. The chief gods honored and worshipped during this month were Chalchihuitlicue, Chicomecoatl, Quetzalcoatl, Tlaloc and Xilonen. Children were taken to the mountains, home of the rain gods, and sacrificed. The dead children were then named in honor of the mountains on which they died.
Sources:
http://www.crystalinks.com/aztecalendar.html
http://www.azteccalendar.com/introduction.html
http://www.davidson.edu/academic/anthropology/ant356/ant356_xihuitl.htm