The relations maintained by the king with the numerous classes of the priesthood was also very close, and the control he exercised over the chief priests and their subordinates appears to have been as effective as that he maintained over the judicial authorities throughout the country. Under the Sumerians there had always been a tendency on the part of the more powerful members of the hierarchy to usurp the prerogatives of the crown,[38] but this danger appears to have been fully discounted under the rule of the Western Semites. One important section of the priestly body were the astrologers, whose duty it probably was to make periodical reports to the king on the conjunctions and movements of the heavenly bodies, with the object of ascertaining whether they portended good or evil to the state. The later Assyrian practice may well have had its origin at this period, and we may conclude that the regulation of the calendar was carried out in accordance with such advice. One of Hammurabi's letters has come down to us in which he writes to inform Sin-idinnam, his local governor of Larsa, that it had been decided to insert an intercalary month in the calendar. He writes that, as the year, that is the calendar, had a deficiency, the month that was beginning was to be registered as the second Elul; and he adds the very practical reminder, that the insertion of the extra month would not justify any postponement in the payment of the regular tribute due from the city of Larsa.[39] The lunar calendar of the Babylonians rendered the periodical intercalation of months necessary, in order that it should be made to correspond to the solar year; and the duty of watching for the earliest appearance of the new moon and fixing the first day of each month, was among the most important of the functions performed by the official astrologers.
In the naming of the year the priesthood must also have played an important part, since the majority of the events from which the years were named were of a religious character. The system, which was inherited from the Sumerians, cannot have been a very convenient one,[40] and no doubt it owed its retention to the sanctity of the religious rites and associations attaching to it. There can be little doubt that, normally, the naming of the year took place at the New Year's Feast, and, when the event commemorated in the formula was the installation of a chief priest or the dedication of temple-furniture, the royal act, we may assume, was performed on the day the year was named.[41] Often merely a provisional title was adopted from the preceding formula, and then perhaps no ceremony of naming was held, unless in the course of it a great victory, or other important occurrence, was commemorated by the renaming of the year. The king must have consulted with his priestly advisers before the close of the old year, and have settled on the new formula in good time to allow of its announcement in the outlying districts of the kingdom.