Letter on the Calendar Controversy

In 921 and 922, a controversy over calculating the Jewish calendar roiled parts of the Jewish world. The Jewish calendar was determined in part by inserting (“intercalating”) an additional day into a month or an additional month into a year, so that the lunar months would stay roughly in step with the seasons. The controversy, in which the Babylonian (“of the Exile”) and Palestinian (“of the land of Israel”) academies vied for the authority to determine the dates, was part of a wider conflict over authority between the two communities. In this excerpt from a long Hebrew letter, Aaron ben Meir outlines his theory of the “Four Gates,” four rules that determined the days of the week upon which Rosh Hashanah could occur; therein, he argued for the authority of the Palestinian gaonate. Aaron also mentions his son, who had announced a new calendrical reckoning. Unbracketed ellipses indicate lacunae in the manuscript.