The distinctive Mayan calendar and Mayan astrology have been in use in Meso-America from at least the 6th Century BCE. There were two main calendars, one plotting the solar year of 365 days, which governed the planting of crops and other domestic matters; the other called the Tzolkin of 260 days, which governed ritual use. Each was linked to an elaborate astrological system to cover every facet of life. On the fifth day after the birth of a boy, the Mayan astrologer-priests would cast his horoscope to see what his profession was to be: soldier, priest, civil servant or sacrificial victim.  A 584 day Venus cycle was also maintained, which tracked the appearance and conjunctions of Venus. Venus was seen as a generally inauspicious and baleful influence, and Mayan rulers often planned the beginning of warfare to coincide with when Venus rose. There is evidence that the Maya also tracked the movements of Mercury, Mars and Jupiter, and possessed a zodiac of some kind. The Mayan name for the constellation Scorpio was also 'scorpion', while the name of the constellation Gemini was 'peccary'. There is evidence for other constellations being named after various beasts, but it remains unclear.  The most famous Mayan astrological observatory still intact is the Caracol observatory in the ancient Mayan city of Chichen Itza in modern day Mexico.
The Aztec calendar shares the same basic structure as the Mayan calendar, with two main cycles of 365 days and 260 days. The 260 day calendar was called Tonalpohualli by the Aztecs, and was used primarily for divinatory purposes. Like the Mayan calendar, these two cycles formed a 52 year 'century', sometimes called the Calendar Round .