Sacha Stern is Professor of Jewish Studies at University College London, and a Fellow of the British Academy. This term he is Visiting Fellow at Princeton University. An ancient historian by training, his research focuses on late antique and early medieval Jewish history, with a focus on the history of calendars and time reckoning, on which he has widely published. Recently he has been working on early Jewish calendar texts preserved in the Cairo Genizah. He has led several research teams and projects funded by the European Commission, the AHRC, the Fritz Thyssen Foundation, the Leverhulme Trust, and other research funding bodies. He is editor of the Journal of Jewish Studies and of two Brill series: Texts and Studies on Time, Astronomy, and Calendars, and Ancient Judaism and Early Christianity.

Toledot Yeshu, a Jewish counter-narrative of the life of Jesus, includes an account of the origins of the Christian liturgical calendar, claiming that the Christian feasts were initially conceived as substitutes for the Jewish feasts. This passage has been dated to the fifth century CE, but I shall argue that it is in fact considerably later. It is of Near Eastern provenance and refers specifically to the East Syriac liturgical calendar, which caused it to be misunderstood when the text was received in early modern Christian Europe.