CHAPTER II. THE OFFICIAL EGYPTIAN CALENDAR. (M20) A useful clue to the original nature of a god or goddess is often furnished by the season at which his or her festival is celebrated. Thus, if the festival falls at the new or the full moon, there is a certain presumption that the deity thus honoured either is the moon or at least has lunar affinities. If the festival is held at the winter or summer solstice, we naturally surmise that the god is the sun, or at all events that he stands in some close relation to that luminary. Again, if the festival coincides with the time of sowing or harvest, we are inclined to infer that the divinity is an embodiment of the earth or of the corn. These presumptions or inferences, taken by themselves, are by no means conclusive; but if they happen to be confirmed by other indications, the evidence may be regarded as fairly strong. (M21) Unfortunately, in dealing with the Egyptian gods we are in a great measure precluded from making use of this clue. The reason is not that the dates of the festivals are always unknown, but that they shifted from year to year, until after a long interval they had revolved through the whole course of the seasons. This gradual revolution of the festal Egyptian cycle resulted from the employment of a calendar year which neither corresponded exactly to the solar year nor was periodically corrected by intercalation.(46) The solar year is equivalent to about three hundred and sixty-five and a quarter days; but the ancient Egyptians, ignoring the quarter of a day, reckoned the year at three hundred and sixty-five days only.(47) Thus each of their calendar years was shorter than the true solar year by about a quarter of a day. In four years the deficiency amounted to one whole day; in forty years it amounted to ten days; in four hundred years it amounted to a hundred days; and so it went on increasing until after a lapse of four times three hundred and sixty-five, or one thousand four hundred and sixty solar years, the deficiency amounted to three hundred and sixty-five days, or a whole Egyptian year. Hence one thousand four hundred and sixty solar years, or their equivalent, one thousand four hundred and sixty-one Egyptian years, formed a period or cycle at the end of which the Egyptian festivals returned to those points of the solar year at which they had been celebrated in the beginning.(48) In the meantime they had been held successively on every day of the solar year, though always on the same day of the calendar.