From Cheikh Anta Diop’s Civilization or Barbarism
Just as with Geometry, the Egyptians were the exclusive inventors of the calendar, the very one which, barley changed, regulates our life today, and about which scientists say “that is the only intelligent calendar that has ever existed in human history”. They invented the 365 day year, breaking it down as follows: 12 months of 30 days, plus 5 days corresponding to the birth of one of the following Egyptian gods (neter): Osiris, Isis, Horus, Seth, and Nephtys. These are the same neter who will give birth to the human race and inaugurate the cycles of historic times: Adam and Eve are only belated Biblical representations of Osiris and Isis.
The year is divided ionto three seasons of four months, the month into three weeks of ten days that do not overlap the months; the day into 24 hours. The Egyptians knew that this calendar year was too short, that was lacking a quarter of a day in order for it to correspond with a complete sidereal revolution. Also, in 4236 B.C. they invented a second astronomical calendar founded precisely on this time lag, this delay, of a quarter of a day per year, in the 365-day calendar year as compared to the sidereal , or astronomical, calendar. The time lag thus accumulated at the end of four years is equal to one day. Instead of adding 1 day every 4 years (a leap year), the Egyptians preferred the masterful solution of following this lag for 1,460 years.
But what is still more amazing is that the Egyptians had equally observed that this period of 1,460 years if the sidereal calendar is the lapse of time that separates the two heliacal rising of Sirius, the most brilliant fixed star in the heavens, and the sun at the latitude of Memphis. Thus, the heliacal rising of Sirius every 1,460 years, coinciding with the first day of the year in both calendars, is the absolute chronological reference point that is the basis for the Egyptian astronomical calendar.
One gets lost in conjecture in order to figure out how the Egyptians were able to arrive at such a result from protohistory, because it is known with certainty that the sidereal calendar was in use from 4236 B.C. onward. Supposing that a celestial phenomenon as fleeting as the rising of Sirius had accidentally caught the attention of the Egyptians from the 4th Millenium onward, or how they couldve guessed at and verified, within a few minutes, its rigorous periodicity, in a time span of 1,460 years, and thus invented a calendar on this basis?? Did they arrive at this result through empirical or theoretical means?The length of the above-mentioned period being in no way comparable to the length of a human life, one has to have magical skills to find an empirical solution to such a problem!
When the Romans conquered Egypt in 47 B.C., Caesar altered the calendar by instistuting the leap year, and that was the origin of the present day calendar.