The majority of recent chronological estimates date Khufu and his pyramid roughly between 2700 and 2500 BC.[37]

Radiocarbon dating
Mortar was used generously in the Great Pyramid's construction. In the mixing process ashes from fires were added to the mortar, organic material that could be extracted and radiocarbon dated. A total of 46 samples of the mortar were taken in 1984 and 1995, making sure they were clearly inherent to the original structure and could not have been incorporated at a later date. The results were calibrated to 2871–2604 BC. The old wood problem is thought to be mainly responsible for the 100–300 year offset, since the age of the organic material was determined, not when it was last used. A reanalysis of the data gave a completion date for the pyramid between 2620 and 2484 BC, based on the younger samples.[38][39][40]
In 1872 Waynman Dixon opened the lower pair of "Air-Shafts", previously closed at both ends, by chiseling holes into the walls of the Queen's Chamber. One of the objects found within was a cedar plank, which came into possession of James Grant, a friend of Dixon. 