MEXICA - not Aztecs
(pronounced "me-shee-ka") History of the Mexica, (Aztecs is a startlingly imprecise term to describe the culture that dominated the Valley of Mexico in the fifteenth and sixteenth centuries.)
http://www.wsu.edu/~dee/CIVAMRCA/AZTECS.HTM
MEXICA HISTORY
The Aztecs, or more properly, the Mexicas, for whom the later Republic of Mexico was named, were a Mesoamerican people of central Mexico in the 14th, 15th and 16th centuries. They were a civilization with a rich mythology and cultural heritage. Their capital was Tenochtitlan, built on raised islets in Lake Texcoco – the site of modern-day Mexico City. The Aztec empire produced the biggest demographic explosion in Mesoamerica: the population grew from an estimated 10 million to 15 million.
http://www.solarnavigator.net/history/aztecs.htm
CALENDAR
http://www.azteccalendar.com/azteccalendar.html
Mexica (Aztec) Calendar converter