Early Egyptians accounted for the year’s “extra” five days (beyond 360) by creating a myth about Nut, a sky goddess.1 According to the story, Nut was allowed to bear a child in “no month of no year.” In answer to her pleading, her lover Thoth played dice with the moon and won an extra five days in the year. He gave them to Nut.
Because these days were outside the old 360-day calendar, the prohibition against Nut bearing children did not apply. Nut’s son Osiris was born on the first of them. Earth-god Geb was said to be the father.
It’s easy to find a similarity between this Egyptian allegory and one written by Plutarch: “Hermes playing at draughts with the moon, won from her the seventieth part of each of her periods of illumination, and from all the winnings he composed five days, and intercalated them as an addition to the 360 days.” 2
In both of these stories the moon is the loosing player. Regardless of the game played, each account claims that the moon’s loss extended the year’s length from 360 to 365 days.
(1) Goudsmit, Samuel A. Time. New York:
Time Incorporated, 1966.
(2) Plutarch. Isis and Osiris (A.D. 75)
Translated by F.C. Babbit.