And the date of 18 April 2647 BC has not been 'invented' by me but by a far more intelligent person: Joseph (Joe) L. Brady who published his astronomical calculations in 1982. His date of 18 April 2647 BC has triggered the Eyptians in the masterplan of the Giza pyramids. Two planets (Jupiter and Saturn) and one star (Regulus) in the constellation of Leo on the day of perihelion passage, the brightest day of visibility of Halley's Comet.
Egyptians feared the return of the metaphorical soul of the King, because they where afraid that He would cause droughts. Kings and Kingdoms are matters of heaven; no matter how anyone tries to 'proof' any existance of 4th dynasty, or earlier, Kings: they will not succeed. No bones; no death kings.
Egyptian Kings are imo avatars. No bones, no bodies. Sealed Royal sarcophagus have been found... when opened...they turned out to be totally empty...
May you're Kingdom come... well, it always has been a matter of the universe and religion. Temples are the palaces of the kings soul when he returns, after 75/76 years, to rule the earth for a couple of weeks upto a couple of months.
So back to the astronomical start: it is 18 April 2647 BC. And not a day later or earlier where the Masterplan, the general lay-out, of Giza has been based upon. And ofcourse they might have used some rules of geometry to define the actual lay-out in the foundation of the three pyramids. In my opinion and for what it is worth.