Dating the site:
Finding the remains of a large community, with as many as 200,000 people living and working together, was a major discovery in itself. But dating the site was a problem. The heavy patina on the rock walls suggested the structures were extremely old, but the science of dating patina is just being developed and is still controversial. Carbon-14 dating of such things as burnt wood introduces the possibility that the specimens could be from recent grass fires which are common in the area.
The breakthrough came quite unexpectedly. As Tellinger describes it:
The first calculations of the age of the calendar were made based on the rise of Orion, a constellation known for its three bright stars forming the "belt" of the mythical hunter.
The Earth wobbles on its axis and so the stars and constellations change their angle of presentation in the night sky on a cyclical basis. This rotation, called the precession completes a cycle about every 26,000 years. By determining when the three stars of Orion's belt were positioned flat (horizontal) against the horizon, we can estimate the time when the three stones in the calendar were in alignment with these conspicuous stars.
The first rough calculation was at least 25,000 years ago. But new and more precise measurements kept increasing the age. The next calculation was presented by a master archaeoastronomer who wishes to remain anonymous for fear of ridicule by the academic fraternity. His calculation was also based on the rise of Orion and suggested an age of at least 75,000 years. The most recent and most acurate calculation, done in June 2009, suggests an age of at least 160,000 years, based on the rise of Orion -- flat on the horizon -- but also on the erosion of dolerite stones found at the site.
Some pieces of the marker stones had been broken off and sat on the ground, exposed to natural erosion. When the pieces were put back together about 3 cm of stone had already been worn away. These calculation helped assess the age of the site by calculating the erosion rate of the dolerite.