The Mayans, and the Aztecs Calender Starts August 13, 3114 B.C. and Ends on December 23, 2112.

THE MAYAN CALENDER

The calender has 20 Sun/glyphs. Is an incredibly accurate map of the cycles of the cosmos.
BASICS OF THE MAYAN SACRED CALENDER
The Mayans have 17 different Calenders based on the Cosmos. Some calenders go back 10 million years. Calenders most important are Haab, Tun-Uc and Tzolk'in. Tzolk'in is the most important and the one with most influence.
Haab, based on cycles of the earth, has 360 + 5 days, - 365 days. The Haab uses 18 months with 20 days in each month. There is a 19th month called Vayeb, uses 5 extra days. Each month has it's own name/glyph. Each day uses a sacred sun/glyph.
Tun-Uc is the moon calendar. Uses 28 day cycles, mirrors the women's moon cycle. This cycle of the moon breaks down into 4 smaller cycles, 7 days each. These smaller cycles are the four phases of the moon cycle. Portal days (p), on the calendar provided marks days using mathematics of 28.
Tzolk'in, the Sacred calender of the Mayans, based on cycles of Pleiadies. The cycle of Pleiadies uses 26,000 years, is in the calender we use - 260 days. Tzolk'in has four smaller cycles called seasons, 65 days each guarded by the four suns of Oc, Men, Chicchan and Ahau. Also, there is portal days within the Tzolk'in that create a double helix pattern using 52 days and mathematics of 28.