The Calendar Controversy of 921/2: Genizah Sources and Historical Reappraisal

In 921/2 CE, a major controversy erupted between the Jews of Palestine and Iraq about how the calendar should be calculated. This led both communities, followed by other Jews in the Near East, to observe Passover and the New Year, in 922, on different dates. It has long been assumed that this was the last dispute of this kind within rabbinic Judaism, and that the triumph of the Iraqi side led to the finalization of the rabbinic Jewish calendar. This scholarly consensus, however, was based on rushed, faulty editions of Cairo Genizah sources that were published in the early 20th century and never revised since.

In the context of an ERC project at UCL on `Calendars in Late Antiquity and the Middle Ages`, the corpus of evidence has been enlarged and completely re-edited, with a focus on establishing correct joins between manuscript fragments, enlarging the corpus with the discovery of additional sources, revising the textual readings, and interpreting the meaning of the sources. As a result, the controversy, its aftermath, and its impact in the following centuries have been radically reappraised. My study sheds light, more generally, on the social and cultural processes that brought about the standardization and fixation of the Jewish calendar in the medieval world.