Another pyramid at Dashur actually has a date on the north-eastern corner stone — it was laid in the 21st year of the
Pharaoh Senefru. About halfway up there is
another date, this time dating to the same PharaohŐs 22nd year. If the dating is accurate, the
maximum between the two would be under two years.
This pyramid is about two-thirds the volume of the Great Pyramid. (Wilson, Crash Go the Chariots, 29)