The first architect of monumental cut stone is lost, or nearly lost, to myth;
the myth we call “Imhotep” may be an accumulation
of attributes and accomplishments made by many people.
However, the step pyramid that he or they designed
broke with precedent in size, shape, and materials of construction.
As for the date of this pyramid,
I take the year that Djoser died.
See also in The book of science:
Readings on wikipedia: