(M24) The reform which the Macedonian king had vainly attempted to impose upon his people was accomplished by the practical Romans when they took over the administration of the country. The expedient by which they effected the change was a simple one; indeed it was no other than that to which Ptolemy Euergetes had resorted for the same purpose. They merely intercalated one day at the end of every four years, thus equalizing within a small fraction four calendar years to four solar years. Henceforth the official and the natural calendars were in practical agreement. The movable Egyptian year had been converted into the fixed Alexandrian year, as it was called, which agreed with the Julian year in length and in its system of intercalation, though it differed from that year in retaining the twelve equal Egyptian months and five supplementary days.(54) But while the new calendar received the sanction of law and regulated the business of government, the ancient calendar was too firmly established in popular usage to be at once displaced. Accordingly it survived for ages side by side with its modern rival.(55) The spread of Christianity, which required a fixed year for the due observance of its festivals, did much to promote the adoption of the new Alexandrian style, and by the beginning of the fifth century the ancient movable year of Egypt appears to have been not only dead but forgotten.(56) CHAPTER III. THE CALENDAR OF THE EGYPTIAN FARMER. § 1. The Rise and Fall of the Nile.