Tzolk'in: Ancient Mayan calendar

The Tzolk'in ...may have been circumstantially significant for agriculture along the south coast of Guatemala. The April 30 zenith transit occurs just before the beginning of the rainy season. Farmers in the region presently plant their corn at the end of April or early in May In August 13 zenith transit the Maya initiate its current era in this day', approximates the time of the harvest of the dried corn.

clipped from en.wikipedia.org Tzolk'in The tzolk'in, the most fundamental and widely-attested of all the Maya calendars, was a pre-eminent component in the society and rituals of the ancient Maya. The Tzolk'in is still in use by several Maya communities in the Guatemalan highlands. Its use is marginal but spreading in this region, although opposition from Evangelical Christian converts has erased it from some communities. The Maya used several cycles of days, of which the two most important were the Tzolk'in, or Sacred Round of 260 days and the approximate solar year of 365 days or Haab. The Sacred Round combined the repeating cycle of numbers 1-13 with 20 day names ... so that any particular combination would recur in 13 x 20 or 260 days; the day name and the number changed together: 1 Imix, 2 Ik, 3 Akbal ... as we might say Monday 1, Tuesday 2, Wednesday 3, and so on