The Maya calendar is a system of calendars used in pre-Columbian Mesoamerica, and in many modern communities in highland Guatemala and in Veracruz, Oaxaca and Chiapas, Mexico. The essentials of the Maya calendar are based upon a system which had been in common use throughout the region. It shares many aspects with calendars employed by other earlier Mesoamerican civilizations, such as the Zapotec and Olmec, and contemporary or later ones such as the Mixtec and Aztec calendars. Although the Mesoamerican calendar did not originate with the Maya, their subsequent extensions and refinements of it were the most sophisticated.