"Gerardo Aldana, associate professor at the Univ. of California at Santa Barbara, challenges the accepted Gregorian dates of all Classic Mayan historical events, including the endoftheworldasweknowit 2012 prophecies in Calendars and Years II: Astronomy and Time in the Ancient and Medieval World, the second in a series edited by John Steele, associate professor of Egyptology and Ancient West Asian Studies at Brown Univ."See Calendars and Years II at Amazon  I have not read the book yet myself.
I have written often before that the Maya calendric chronology as falsely interpreted by Maya scholars is off for the reasons identified by me here.
I wrote there the following:
THE MAYA CALENDAR
PIEDRAS NEGRAS
HALLEY'S COMET
PIEDRAS NEGRAS
HALLEY'S COMET
Just as in the
Pharaonic Egyptian calendar
December 25, 3117 BC is the correct starting date for the Maya calendar (corrected for the tropical year), as will be demonstrated below.
Maya scholars have
failed to adjust the continuous count of solar days of the Maya Long
Count to a "longer" count including intercalation for the tropical
year. When this adjustment is made, the Maya and Pharaonic calendars
both start on December 25, 3117 BC (3116 by astronomy).
Maya scholars start
the Maya calendar
on a Maya date called 4 Ahau 8 Cumku. Both of these calendric glyphs (Ahau and Cumku) fall at the "end" of the Maya series of days and months in the Maya system, i.e. at the beginning of new eras, and we thus expect a Solstice or Equinox at this point in Maya calendration. Indeed, the Encylcopaedia Britannica writes at "Calendar" about the Maya system as follows:
"The 365day
year was divided into 18 named months of 20 days each, with an
additional five days ... named Uayeb. In late times, the Maya named the
years after their first days. Since both the year and number (20) of
the names of days are divisible by five, only four names combined with
13 numbers could begin the year. These were called Year Bearers and
were assigned in order to the four quarters of the world with their
four associated colours."
The calendar, with adjustments for the tropical year, starts on Julian date 583297. The Maya Calendar allegedly started on Julian date 584283. The Maya date is correlated to the alleged foundation of Merida, Yucatan on November 14, 1539 close to the date of the Long Count Maya katun 11.16.0.0.0 = 11 baktuns, 16 katuns, 0 tuns, 0 uinals, and 0 kins.
In Maya chronology,
1 baktun = 144000 days, 1 katun = 7200 days, 1 tun = 360 days, 1 uinal
= 20 days, 1 kin = 1 day. The Maya Data 11.16.0.0.0 as a
chronological date thus involves the following calculation:
11 x 144000 days (=1584000 days) + 16 x 7200 days (=115200 days) = 1699200 days i.e. 1699200 continous solar days have elapsed since the Long Count katun 0.0.0.0.0. This is a continous count WITHOUT adjustment for the tropical year. Let us now adjust that figure for the tropical year  which will give us the correct "astronomical", i.e. "star date". How many 365day years are there in 1699200 days? = 4655 years. BUT, 4655 years of ca 365.25days (actually 365.22 days) = 1700238 days rather than 1699200 days. 1700238 days plus the Julian date 583297 (Dec. 25, 3117 BC) as the start of the calendar gives Julian date 2283535 and that is in fact the expected Solstice date, December 25, 1539 AD at Merida. The Merida "Maya" date of November 14, 1539 AD should thus actually be December 25, 1539 AD, and that is the correct Long Count Maya katun 11.16.0.0.0. The 365day year katun date must simply be converted to 365.25day years, which gives an identical starting date to the Pharaonic Calendar. They ARE related. Did the Maya Adjust Their Calendar for the Tropical Year? Were the Maya themselves aware of this potential error in their calendration? Did they make intercalary notations as "leapyear type of periods" between the solar and tropical years in their system? Yes  as demonstrated here  they did. In fact, they had apparently adjusted for it periodically. As the Encyclopaedia Britannica notes, the Maya used an "InitialSeries" notation (abbreviated IS) on its dates, referring the marked date back to the start of the calendar. The oldest known such IS (Initial Series) notation is Stele 29 at Tikal in Guatemala which is written IS. 8.12.14.8.15, a date which falls 1243615 days after the start of the calendar at 4 Ahau 8 Cumku. Can we determine when that was? We can. Often in Maya dating of the socalled Supplementary Series, the socalled IS (Initial Series date) is preceded by a notation of 819 days. This notation of 819 days is thought by Maya scholars to be merely a magical multiple of 13, 9 and 7, which equals 819. But as shown here for the first time, these 819 days are the intercalation for the tropical year. This intercalation was apparently made at Tikal, Guatemala on January 25, 293 (Julian date 1828100) and used in the Supplementary Series of dates. The Tikal IS (Initial Series) date of 1243615 days after the start of the Maya calendar is a sum of 3407.16438 years of 365days whereas 1243615 days of ca. 365.2422day years equals 3404.90501 years, a difference of ca. 2.25 years, which is ca. 820 days, i.e. the intercalary figure of 819.
Thus, these 819
days were added to the continuous solar day count on January 25, 293 AD
for the Maya Supplementary Series of dates. The continous count itself
was not intercalated.
The Pharaonic and
Maya calendars both started
on December 25, 3117 BC viz. 3116 by astronomy. The 293 AD date at Tikal was probably chosen because it involved 48 years of intercalation for precession  i.e 48 degrees of precession x 72 years = 3456 years so that 3116 BC + 293 AD= 3409 years total and 3409 + 48 = 3457 years.
USE OF THE METONIC
CYCLE
How did the Maya,
the Hebrews, the Pharaohs
and the Vedic Sanskrit Hindus use the Metonic Cycle for longterm calendration? It is very simple once one sees the numbers, which allow very accurate calculations  without fractions or decimals  using the principle of common denominators. 
Period

multiplied by

= number of days  divided by 
= days

calendric use

3800 years 
x 360 days

= 1368000 days 
/ 19

= 72000  = half a Baktun 
3800 years 
x 365 days

= 1387000 days 
/19

= 73000 
solar years

3800 years  x 365.25 days  = 1387950 days 
/19

= 73050 
star years

Since a complete Maya baktun is 144000 days
(compare to the halfBaktun of 72000 days in the line above),
a full cycle of the above system is 100 x 76 years = 7600 years.
7600 years are 2736000 days of a
schematic 360day year
which equals = 19 Baktuns. This formed the Maya calendar.
It made calendration easy by common divisors.
which equals = 19 Baktuns. This formed the Maya calendar.
It made calendration easy by common divisors.
19 Baktuns  = 380 Katuns  /19  = 20  /20  = 1  
380 Katuns  = 7600 tuns  /19  = 400  /20  = 20  / 20  = 1  
7600 Tuns  = 136800 uinals  /19  = 7200  /20  = 360  / 20  = 18  /18  =1 
136800 Uinals  = 2736000 days  /19  =144000  /20  = 7200  / 20  = 360  /18  =20 
.MAYA STELE 3 PIEDRAS NEGRAS
CORRECTED READING
The Corrected
Reading of Maya Stele 3 of Piedras Negras
This corrected
reading of the CholMaya Stele 3 of Piedras Negras
is based on my discovery of the 819day intercalation for the tropical year made at Tikal, Guatemala and the recognition that the Maya Calendar begins on December 25, 3117 BC. This article adds evidence to the correctness of that date.
The current reading
of Maya Stele 3 of Piedras Negras [with glyphs] by Maya scholars is
found in Michael D. Coe's book Breaking the Maya Code,
pp. 368372 of the German version Das Geheimnis der MayaSchrift.
This Stele is
erroneously thought to apply to the birth and life of a "human" female
called Katun Ahau and her daughter Kin Ahau, but it is actually a stele for the "birth" of a new CALENDRIC Katun Ahau.
As noted at the end
of Stele 3 Piedras Negras, the new Katun Ahau
began on 9.14.0.0.0 .. 6 Ahau 13 Muan, which was 1396800 days after December 25, 3117 BC or 583297 + 1396800 = Julian date 1980097 which is March 19, 709 AD, exactly at the point where the Sun is at the crossing of the Celestial Equator and the Ecliptic.
The Piedras Negras
date of 9.12.2.0.16 .. 5 Cib 15 Yaxkin
at the start of Stele 3 is NOT the date  as reported by Coe  of July 7, 674 AD, but is rather October 21, 671 AD.
The Maya Stele 3
Piedras Negras date
is correctly calculated as 9 x 144000 days plus 12 x 7200 days + 2 x 360 days + 0 + 16 days = 1296000 + 86400 + 720 + 0 + 16 = 1383136 days.
This date is a
continuous solar count without intercalation
so it is added to the Julian Date for the start of the Maya calendar (December 25, 3117 BC), i.e. Julian Date 583297 which  added to 1383136  gives a Julian Date of 1966433, or October 21, 671 AD for Stele 3 at Piedras Negras. This is Libra, the Maya NAH, 7th night station,  which puts on its "headband"  the term NAH perhaps found in Chinese as Se HAN, and Semitic MizNAIm "Libra".
The stele states
further that it was 27 days after the Full Moon
at the Vernal Equinox (the cross of the Celestial Equator and Ecliptic) at Spica in Virgo  this was Julian date 1966406 on September 24, 671 AD.
Two months of 29
days after Julian date 1966433 pass and the
"three white mountain god" appeared: This is the prong of Sagittarius on December 18, 671 AD on Julian date 1966491 [Since there is an apparent error of 44 days later, it may be that not 58 days are added here but only 14, since 58  14 = 14 would take care of the error. The end result, however, stays the same.]
14 Yaxkin.
10 Uinal and 12 Tun
pass
10 x 20 = 200 days and 12 x 360 = 4320 days = 4520 days 4520 added to 1966491 = Julian date 1971011 or Maya date 9.12.14.13.14 .. 1 Cib 14 Kankin
This (1971011) puts
the Sun at the Pleiades on May 3, 684 AD
where she is decorated with the great Sun, Yo' Acnal. [There is a conjunction here with Jupiter at this date and a New Moon at the Pleiades on April 20, 684 AD, Julian date 1970998.]
10 Kin 11 Uinal 1
Tun and 1 Katun pass (4 Cimi 14 Uo)
10 x 1 = 10, 11 x 20 = 220, 1 Tun = 360= 590 days total 1 Katun = 7200 days = 7790 days Kin Ahau was allegedly born on August 31, 705 AD, Julian date 1978801 at Virgo. The stele calls this the tortoise of heaven.
14 Kin 8 Uinal and
3 Tun pass ... 11 Imix 14 Yax
14 x 1 = 14, 8 x 20 = 160, 3 x 360 = 1080 = 1254 days This is February 5, 709 AD Julian date 1980055 at Aquarius.
The Stele states
that 5 Tun and 1 Katun have passed
since the beginning of the rule of Yo'Acnal so that 5 x 360 = 1800 and 1 x 7200 = 7200 so that 1800 + 7200 = 9000 days. but 7790 + 1254 above give 9044 days.
The stele
then states at this point that 9000 days have passed
since the start of the rule of Yo´Acnal (rather than 9044). Hence rather than 1980055 the 9000 days end 44 days previously at Julian day 1980011 which is 9000 days after 1971011, The Winter Solstice at December 23, 708 AD.
19 Kin and 4 Uinal
pass ... 6 Ahau 13 Muan
19 x 1 = 19 and 4 x 20 = 80 = 99 days These are apparently calculated from Julian day 1980011 1980011 plus 99 days = 1980110 This gives a date of April 1, 709 AD. If the 9000 days are calculated back to the Sun at the Pleiades this then gives a date of March 19, 709 AD. This is the date given for 9.14.0.0.0 .. 6 Ahau 13 Muan at the very beginning of this article.
The stele closes by
writing
6 Ahau 13 Muan ends. The 14th Katun begins. 
.FURTHER PROOF
HALLEY'S COMET AND MAYA CHRONOLOGY
The current Maya chronology includes a spectacular event called the Entrada of 378, for the arrival at Tikal of a lord called Siayaj K'ak' (meaning and translated "Fire Born" by the Mayanolgists), dated to January 31, 378 by the Mayanologists.
At the same time, the "king" Chak Tok Ich'aak allegedly passed away on January 15, 378 (8.17.1.4.12)  whose name means "Great Burning Claw". This Entrada (Entrance) of Siyaj K'ak' took place on January 31, 378 according to mainstream Mayanology  indeed, the appearance of this mysterious "fire born" is documented 8 days earlier and his "route" is even traced in Maya records.
Now  if this were a HEAVENLY BODY it would be a fiery comet  AND it is a comet, Halley's Comet, which came very close to earth in what the serious astronomers today estimate to be 374 A.D. According to MY chronology, the Maya date January 31, 378 is correctly May 4, 375 A.D. and this is the Maya record of the sighting of this very near passage of Halley's Comet, one of the closest to Earth on record.
We find Halley returns at ca. 76year multiples in the names of Maya "rulers".... though all the mainstream dates are off by the error of 2+years in mainstream chronology which I have discussed above.
Halley is the Accession of K'an Chitam in 458 A.D.  actually, this was 2+ years earlier. Ruler "Bird Claw?"  also known as "Animal Skull I"  this is Halley again  is dated by Mayanologists to between ca. 527 and 537 A.D.
Ca. 76 years we then have Halley again as Animal Skull II.
Halley appears again as the illustrious king Yich'aak K'ak' (Fiery Claw) whose "flint and shield" are brought down by Jasaw Chan K'awiil I on (sic) August 5, 695 A.D.  but of course this is 2+ years earlier in fact.
So, Halley has been clearly identified, and mainstream Maya chronology is off by the period of time I have previously described in great detail in other LexiLine postings.
HALLEY'S COMET AND MAYA CHRONOLOGY
The current Maya chronology includes a spectacular event called the Entrada of 378, for the arrival at Tikal of a lord called Siayaj K'ak' (meaning and translated "Fire Born" by the Mayanolgists), dated to January 31, 378 by the Mayanologists.
At the same time, the "king" Chak Tok Ich'aak allegedly passed away on January 15, 378 (8.17.1.4.12)  whose name means "Great Burning Claw". This Entrada (Entrance) of Siyaj K'ak' took place on January 31, 378 according to mainstream Mayanology  indeed, the appearance of this mysterious "fire born" is documented 8 days earlier and his "route" is even traced in Maya records.
Now  if this were a HEAVENLY BODY it would be a fiery comet  AND it is a comet, Halley's Comet, which came very close to earth in what the serious astronomers today estimate to be 374 A.D. According to MY chronology, the Maya date January 31, 378 is correctly May 4, 375 A.D. and this is the Maya record of the sighting of this very near passage of Halley's Comet, one of the closest to Earth on record.
We find Halley returns at ca. 76year multiples in the names of Maya "rulers".... though all the mainstream dates are off by the error of 2+years in mainstream chronology which I have discussed above.
Halley is the Accession of K'an Chitam in 458 A.D.  actually, this was 2+ years earlier. Ruler "Bird Claw?"  also known as "Animal Skull I"  this is Halley again  is dated by Mayanologists to between ca. 527 and 537 A.D.
Ca. 76 years we then have Halley again as Animal Skull II.
Halley appears again as the illustrious king Yich'aak K'ak' (Fiery Claw) whose "flint and shield" are brought down by Jasaw Chan K'awiil I on (sic) August 5, 695 A.D.  but of course this is 2+ years earlier in fact.
So, Halley has been clearly identified, and mainstream Maya chronology is off by the period of time I have previously described in great detail in other LexiLine postings.