The most significant development in the rabbinic calendar of the first millennium ce was its transition from an empirical system to a fixed, calculated scheme. This change has been described in some detail in the previous chapter; but why it occurred remains entirely to be explained.
The traditional explanation is that the fixed calendar was instituted because of persecutions and unfavourable political conditions. This theory, together with others, will be assessed in detail in this chapter. It will become clear that the change that occurred to the rabbinic calendar was less the result of external pressures than of internal historical processes. As I shall argue, the emergence of the fixed rabbinic calendar went hand in hand with the development of the rabbinic community of the late Roman period.
One of the distinctive characteristics of the rabbinic community in late Antiquity and the early Middle Ages was its gradual geographic expansion. From being mostly confined to Judaea until the early second century ce, the rabbinic community had spread to Galilee by the middle of this century, after the Bar-Kokhba revolt of 132-5 ce;it then spread to Babylonia in the early third century, with the first generation of Amoraim. In the course of the Geonic period, rabbinic Judaism was to expand further afield to Egypt, North Africa, and southern and western Europe, and eventually to dominate the whole of world Jewry. Throughout this period of expansion, the question of solidarity, cohesion, and communitas between the various rabbinic communities became increasingly pressing. In this context, I shall argue, the calendar came to play a decisive role. The institution of a standard, fixed calendar was a significant contributor to the unity of the rabbinic community or—as the rabbis saw it—of the Jewish people.