To seek the Truth :

For I wish to point out that the emotional creed of educated men is becoming divorced from their scientific creed ; that just as the old orthodoxy of religion was too narrow to contain mens knowledge , so now the new orthodoxy of materialistic science is too narrow to contain their feelings and aspirations , and consequently that just as the fabric of religious orthodoxy used to be strained and overpassed in order to admit the discoveries of geology or astronomy , so now also the obvious deductions of materialistic science are strained and overpassed in order to give sanction to feelings and aspirations which it is found impossible to ignore . 

Frederic  Myers 

Egyptian astronomy had much less influence on the outside world for the very simple reason that it remained through all its history on an exceedingly crude level ...

Otto Neugebauer

The contrary happens in Egypt, for there monuments exist more ancient that any of the inscribed records ; monuments indicating a more or less settled civilisation ; a knowledge of astronomy and temples erected on astronomical principles for the purposes of worship , the astronomers being called "the mystery teachers of Heaven".

Sir  Norman Lockyer

Where is the Truth ?

Was the Great Pyramid built about 20,000 years BP ?

The obliquity of the ecliptic (eps), or inclination of the Earth's axis of rotation, is the angle between the ecliptic and the celestial equator.
There are the mean and the true obliquity, the first term indicates that the correction for nutation is not taken into account.
It is known empirical formula of cyclic variation of the mean obliquity of the ecliptic during long period of time which was first constructed by Newcomb (1906) and hence it is possible to find the possible time of construction of the monuments.
The main period is around 41,000 years and maximum amplitude is around +/- 1.3 degrees.
This method was first used by Lockyer for determination age of Stonehenge (1909), and then, Posnansky with Müller used it for investigation of age Tiahuanaco (1930).
Current work uses modern numerical expressions for the mean obliquity of the ecliptic by two models of Edwardsson (2002) and Bretagnon (2003).