Aleph: Historical Studies in Science and Judaism

ABSTRACT:

The correct way of setting the calendar was a matter of much debate among medieval Jews. While it is well-known that medieval Rabbanite and Qaraite communities practiced different calendars, the Jewish calendar landscape of the ninthtenth centuries appears to have been much more diverse. Medieval sources suggest that Jewish groups in that period used calendars based on a variety of principles including observation, different calculations, and a combination of observation and calculation. No in-depth examination exists of medieval alternatives to the Rabbanite calendar. This article is a study of non-Rabbanite medieval Jewish calendars described in tenth-century Babylonian works the Kitāb al-Tamyīz and the Commentary on Genesis by Saadia Gaon, and Kitāb al-Anwār wal-Marāqib by Jacob al-Qirqisānī. In addition to analysing the calendation methods described in the sources, I assess the trustworthiness of Saadia and al-Qirqisānī’s reports and suggest that they reflect real calendars of the period with some degree of accuracy.