Teeple
assumed that if these inscriptions record lunar ages supposedly in the
mythological past, they would have been contrived by the
scribes, and thus consistent with each another. If his hypothesis
about the meaning of the supplementary series was correct, he
expected to find that his readings of the moon ages would be 14 days
apart.
He read the Temple of the Sun glyphs as a
record of a
moon age of 26 days, in the 4th lunar month, which was 30 days
long. Thus the Temple of the Foliated Cross should record a moon
age of 10 days, in the 5th lunar month, which would be 30 days
long. This is in
fact the information recorded by the supplementary series in the Temple
of the
Foliated Cross inscription.
Both Yaxchilan Lintel 21 and Quirigua Zoomorph P record dates
in the
Classical era, and report accurate lunar ages.
The Palenque inscriptions record lunar ages in 2360 BC. These lunar
ages
were likely calculated by subtracting multiples of lunar months from a
base date near the time the temples were erected in 690 AD. Error
in the estimate of the length of the month cumulates in calculations
such
as this. In the result, the lunar ages from the mythological past are
in
error by about 8 days.
Monuments that record historical rather than mythological
dates were
usually erected a decade or more after the long count date inscribed on
them. The scribes often relied on calculation to determine the lunar
age
counts required for the inscriptions, back dating from an
observed lunar
age by subtracting multiples of the lunar month. Six lunar months is
very
close to a whole number of days. Since lunar months were counted in
series
of 6, it is likely that the formula 6 lunar months = 177 (29.5 x
6) days was used in calculating lunar ages. However, the true
length
of the synodic period of the moon is 29.53059 days. Thus this
method
of calculation introduces an error of about 0.36 days per year.
Teeple
found that the lunar ages in inscriptions are often in error by a few
days.
After studying lunar ages recorded on monuments at Copan, he concluded
that many of the errors in recorded lunar ages result from use of this
approximation.
More accurate multiples of the lunar month were
sometimes used
for long range calculations. Comparison of Classical lunar ages in
Palenque
monuments with the mythological lunar age from the Temple of the Sun
suggests
that the latter was calculated using the formula 81 moons =
2,392 days. This gives an average length of the lunar month of
29.53086,
accurate to within 7 minutes. While not accurate enough to calculate a
lunar age over two thousand years in the past, this formula would have
produced accurate results when used to calculate lunar ages in the
Classical
era. At Copan, a formula that was almost as accurate seems to have been
known: 149 moons = 4400 days. This gives a value of the lunar month of
29.5302 days.
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The last glyph block
in the lunar series
invariably includes a glyph with an infixed circular element. It is
always associated with the number 9 (bar and four dots) or ten (two
bars). Because the haab date usually follows it, before
the function of the lunar series was known, this glyph was dubbed the "haab
indicator." Its presence is the easiest way to verify that an
inscription
contains lunar information. The example below begins with an
initial series date, records a lunar age of 7 days, and ends with the
"haab indicator" and number nine.
The
most confusing forms of Glyph D look all too much like Glyph E,
but
usually differ on close inspection: The circular element has more
than one central "dot", or the "dot" is not circular. This form
of
glyph D likely reads u, "moon". This confusion
has
led some epigraphers to read the lunar age in the Yaxchilan inscription
as 27 days rather than 7 days. However, on the long count
9.0.19.2.4
(16 October 454 AD), the moon was actually close to 7 days
old.
A 20 day error does not seem likely.
Name
of the Lunar Month (Glyphs B and X). Glyph B appears to name the
lunar
month, though most of the names have not yet been securely translated.
Glyph X is not
always
present, but takes a fairly standard form. It is a combination of
phonetic symbols which spell u k'a ba, "is its
holy name." 