Mesoamerica movements of celestial bodies and memorialize public officials. The 260-day cycle was also used for divination, and (like the Catholic calendar of saints) to name newborns. The names given to the days, months, and years in the Mesoamerican calendar came, for the most part, from animals, flowers, heavenly bodies, and cultural concepts that held symbolic significance in Mesoamerican culture. This calendar was used throughout the history of Mesoamerican by nearly every culture. Even today, several Maya groups in Guatemala, including the [[K'iche' people|K'iche']], [[Q'eqchi' people|Q'eqchi']], [[Kaqchikel people|Kaqchikel]], and the [[Mixe]] people of Oaxaca continue using modernized forms of the Mesoamerican
Mesoamerican calendars menstrual period and birth, unlike Naegele's rule which is 40 weeks (280 days) between the "last" menstrual period and birth. It is postulated that midwives originally developed the calendar to predict babies' expected birth dates. A third theory comes from understanding of astronomy, geography and paleontology. The mesoamerican calendar probably originated with the Olmecs, and a settlement existed at Izapa, in southeast Chiapas Mexico, before 1200 BCE. There, at a latitude of about 15° N, the Sun passes through zenith twice a year, and there are 260 days between zenithal passages, and gnomons (used generally for observing the path of