Ancient Egypt | Herodotus History Etext
Egyptians made important advances in the accuracy of the calendar. The fifth century B.C. Greek historian Herodotus says the Egyptians were the first ones to divide the year into 12 parts (our months) based on their observation of the stars. He argues their calendar is wiser than that of the Greeks. Four centuries later, it took an Alexandrian mathematician Sosigenes to help Julius Caesar reform the Roman calendar (creating the Julian calendar) in 46 B.C. Diodorus Siculus (fl. 1st century B.C.) (Book I.9) also credits the Egyptians with astronomical science: "And since Egypt is the country ... where the earliest observations of the stars are said to have been made...."
The following is the relevant passage, from a public domain translation of Herodotus by G. C. Macaulay Book II
4. But as to those matters which concern men, the priests agreed with one another in saying that the Egyptians were the first of all men on earth to find out the course of the year, having divided the seasons into twelve parts to make up the whole; and this they said they found out from the stars: and they reckon to this extent more wisely than the Hellenes, as it seems to me, inasmuch as the Hellenes throw in an intercalated month every other year, to make the seasons right, whereas the Egyptians, reckoning the twelve months at thirty days each, bring in also every year five days beyond the number, and thus the circle of their seasons is completed and comes round to the same point whence it set out. They said moreover that the Egyptians were the first who brought into use appellations for the twelve gods and the Hellenes took up the use from them; and that they were the first who assigned altars and images and temples to the gods, and who engraved figures on stones; and with regard to the greater number of these things they showed me by actual facts that they had happened so.
