Parsing out the two scenarios (see previous post for the context).
Scenario number 1. The astronomers and scribes associated with the court of Lord Jaguar are working to craft his rhetoric of power. All kings need this. He is a reformer and within months of his accession to rulership in 644 AD he launched his first war campaign. He then proceeded to kick butt at lightning speed over the next five years, vanquishing four regional kingdoms. He restored the region to a semblance of its former glory, before the two wars that decimated neighboring Palenque decades earlier. In these victories, Lord Jaguar defined himself as a transformational agent, a vehicle of power and renewal. His persona was not unlike the Hero Twins who vanquished the Lords of the Underworld to pave the way for a new Era with the resurrection of their father, One Hunahpu. And in late 649, Lord Jaguar was bestowed with a priestly honor as he reframed his role as king, embracing the duties of sacrificial priest while performing a version of the Creation Myth.
By 669 AD a Katun had elapsed since his year of victory. He was approaching his 57th year and it was time for his reign and his victories to be documented in a powerful rhetorical statement. His rhetoricians knew that they must try to relate his personal life to the larger framework of the Creation Mythos. They considered his accession date, his birthday, and other circumstances of his personal identity. They noticed that when he was born the sun was positioned at the Crossroad of the Milky Way and the ecliptic, at the entrance to the Dark Rift. They saw this as significant, because those features just happened to be part of the ancient Creation Myth.
They continued randomly casting about for tidbits of useful rhetoric. The Long Count calendar was sometimes useful. They projected forward to look for things, to the end of the 10th Baktun, some 160 years into the future. Nothing much. So they projected to the ends of the 11th, 12th, and 20th Baktuns, and so on. Finally, they noticed something about the astronomy of the future end of the 13th Baktun. It was just a happy coincidence that the number 13 was involved. Because the astronomers had recently perfected an ability to calculate the Sidereal Year and the Tropical Year, Lord Jaguar’s scribes and priests could calculate the sun’s position on the future 13th Baktun ending, 18.104.22.168.0 in the Long Count. To their utter amazement, they noticed that the sun was positioned in the exact same position as it was one Lord Jaguar’s birthday! This was a Sidereal Year calculation. Moreover, they also calculated that it would be the date of the solstice turnabout in winter. This was a Tropical Year calculation.
They wondered at the amazing coincidence of this part of the sky being involved in a rare astronomical alignment, since that part of the sky was important in their Creation Myth and yet there was absolutely no tradition about this alignment being known to the ancient creators of the Long Count. They had accidentally stumbled upon a perfect rhetoric narrative for Lord Jaguar’s victories.
The Long Count had been being followed for over 700 years by this time. A 13th Baktun ending had already been written about by the priests of Copan, far to the south. But that was the previous 13th Baktun ending, some 3800 years earlier. Somehow, the Copan priests decided that a 13-Baktun period was important in the Long Count, even though there was no tradition about it. Well, “whatever”, thought Lord Jaguar’s priests. The may have ruminated as follows: “It is astounding that we have just accidentally discovered such a rare alignment with the new knowledge of the astronomical cycles that we have recently perfected, and that it occurs on the solstice, and at the Crossroads of our ancestor’s Creation Myth, and on the future 13th Baktun ending, that also corresponds to the astronomy of Lord Jaguar’s birthday. Such an astounding coincidence of many different threads must be a gift from the gods.”
That was scenario number one. Scenario number 2 is that within the lore and ancient knowledge preserved by Lord Jaguar’s priests, it was known that the future 13th Baktun would have those alignment characteristics, because the placement of that date within the structure of the Long Count was intended by the creators of the Long Count. It may be that Lord Jaguar was born close to the same alignment, and that his birthday was fudged slightly for the rhetorical narrative. Or perhaps he was born on the correct day and for that reason he was seen to be divinely selected and was preferentially nurtured to take on the needed role of reformer. That would be the only coincidence, or near-coincidence, in this scenario, compared with four coincidences in the first scenario.
It perhaps took the eventual, and inevitable, near congruence of a king’s birthday with the mythologically potent solar position of the Dark Rift / Crossroads, throughout hundreds of years of the Classic Period, for the ancient knowledge to be finally stated in a rhetorical narrative of a king and preserved for posterity. Once the cat was out of the bag, the narrative complex was used in various ways in other narratives, for example on the tablet from Palenque’s Temple of the Cross (690 AD). Which scenario sounds more reasonable to you?