(M78) The festival of Osiris which Plutarch assigns to the month of Athyr would seem to be identical in substance with the one which the inscription of Denderah assigns to the following month, namely, to Khoiak. Apparently the essence of both festivals was a dramatic representation of the death and resurrection of the god; in both of them Isis was figured by a gilt cow, and Osiris by an image moulded of moist vegetable earth. But if the festivals were the same, why were they held in different months? It is easy to suggest that different towns in Egypt celebrated the festival at different dates. But when we remember that according to the great inscription of Denderah, the authority of which is indisputable, the festival fell in the month of Khoiak in every province of Egypt, we shall be reluctant to suppose that at some one place, or even at a few places, it was exceptionally held in the preceding month of Athyr, and that the usually well-informed Plutarch described the exception as if it had been the rule, of which on this supposition he must have been wholly ignorant. More probably the discrepancy is to be explained by the great change which came over the Egyptian calendar between the date of the inscription and the lifetime of Plutarch. For when the inscription was drawn up in the Ptolemaic age the festivals were dated by the old vague or movable year, and therefore rotated gradually through the whole circle of the seasons; whereas at the time when Plutarch wrote, about the end of the first century, they were seemingly dated by the fixed Alexandrian year, and accordingly had ceased to rotate.(201)