Maya Calendar

The Maya calendar is a system of distinct calendars and almanacs used by the Maya civilization of pre-Columbian Mesoamerica, and by some modern Maya communities in highland Guatemala.
These calendars can be synchronized and interlocked in many ways, their combinations giving rise to further, more extensive cycles. The essentials of the Maya calendric system are based upon a system which had been in common use throughout the region, dating back to at least the 6th century BCE. 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. Along with those of the Aztecs, the Maya calendars are the best-documented and most completely understood.
By the Maya mythological tradition, as documented in Colonial Yucatec accounts and reconstructed from Late Classic and Postclassic inscriptions, the deity Itzamna is frequently credited with bringing the knowledge of the calendar system to the ancestral Maya, along with writing in general and other foundational aspects of Maya culture

Maya Calendar
The Maya developed a sophisticated calendar. The ritual calendar that developed in Mesoamerica used a count of 260 days. This calendar gave each day a name, much like our days of the week. There were 20 day names, each represented by a unique symbol. The days were numbered from 1 to 13. Since there are 20 day names, after the count of thirteen was reached, the next day was numbered 1 again. The 260-day or sacred count calendar was in use throughout Mesoamerica for centuries, probably before the beginning of writing.

The Maya also tracked a vague solar year in which they counted 365 days per year. Because they could not use fractions, the "quarter" day left over every year caused their calendar to drift with regard to the actual solar year. The 365-day year contained months were also given names. numbers 0-19 before they changed, so that the count goes Zero Pohp to 19 Pohp, then continues with Zero Wo.