The 19th of July by the Julian calendar (the 15th of June by the Gregorian), 4241 B.C., on which the 365-day calendar was introduced in lower Egypt, is the oldest certain date in history.¹

¹Meyer, E.n/an/an/an/an/a, , §197.

[Meyer’s calculation is based on evidence that the Egyptian new year was fixed by the coincidence of the spring overflow of the Nile and the heliacal rising of the star Sirius. One of these conjunctures was in the year 2781 B.C., but the sacrifice formulas and the pyramid texts show that the calendar was already in use at this date. Meyer therefore assumes that the calendar was fixed at the next older date, which was in the year 4241 B.C.]