- Reference for determining the Moon's Age (like: an observed
New Moon; a calculate New moon; a known base from Maya Creation
Date [aka 0.0.0.0.0]).

A few more parameters are needed to determine this further: - the date how New Moon is defined

Depending on several definitions: observed/calculated first/last/average crescents or fixed at Maya Creation Date - length of the lunar synodic period

Copan's Synodic period [29.5302 days]; Palenque's Synodic period [29.53086 days] (Linden [1986], page 126); or the modern Synodic period - the Moon's
Age value at Maya Creation Date

Copan [22 days]; Palenque [24 days] (both mentioned by Teeple [1931], page 68); or like on the Coba stela 1 [23 days] (Stone [2010], page 44) - The month's length determination

By observation [some 5 methods are implemented, related to how New Moon was determined] or by the*18 month lunar synodic calendar*(Linden [1993], page 350).

- The Correlation
(like GMT) between Maya calendar and Julian Day Number.

In the below no reference is made to the Julian Day Number as the Maya Creation Date, 0.0.0.0.0, and the Moon's Age at that date are used, so the Correlation is not important in this case.

If one uses: the

Coba Stela 1 has a D/E glyph of 23 [

If one uses the Palenque Moon's Age of 24 days at Maya Creation Date [

So it looks that the Moon's Age at Maya Creation Date could be the reason for the non-zero mean of the difference distribution. Should it be close to zero or not?

So what is this Moon's Age at Maya Creation Date and how sure are we about its value?

Teeple [1928] recognises three periods: Period
1 (Independence), Period 2 (Unity) and Period 3 (Revolt).

If one puts all the differences between glyph and calculation in a
graph, one can determine if the differences change over time:

Period 2 indeed seems to have somewhat less variations (as expected for the Unity period), but it is not that significant. In the below figure the 1 sigma of the differences has been calculate over groups of 10 dates, and one can see there is no significant reduction of this variation around Period 2:

- The Maya Creation Date 0.0.0.0.0 as a reference

- The Copan Synodic period of 29.5302 days; which was also
used during the Unity period (Teeple [1931], page 68)

- The Palenque Moon's Age at Maya Creation Date of 24 days

Somewhat controversial related to the Copan Synodic period length! If you have feedback, let me know.

- The
*18 month lunar synodic calendar*of Linden [1993] - In general this is working for Teeple [1928]'s Periods 1,
2 and 3.

John E. Teeple. "Maya Inscriptions VI: The lunar calendar and its relation to Maya history." American Anthropologist 30, no. 3 (1928): 391-407.

John E. Teeple. Maya astronomy. Vol. I-4, Contributions to American archaeology. Washington: Carnegie Institution of Washington, 1931.

John Linden. "Glyph X of the Maya lunar series: An Eighteen-Month Lunar Synodic Calendar." American Antiquity 51, no. 1 (1986).

John Linden. "The deity head variants of Glyph C." Paper presented at the Eighth Palenque Round Table, San Francisco, 1993.

Mark Van Stone. 2012: Science and Prophecy of the Ancient Maya: Tlacaelel Press, 2010.

Major content related changes: Sept. 5, 2012