An Easter cycle in Hebrew from 725 CE

A fragmentary manuscript from the Cairo Genizah (T-S NS 98.51) contains a description in Hebrew of the Julian calendar, how to calculate its dates, and a 19-year Easter cycle, all in the Byzantine tradition of calendar computation. The Easter cycle is presented in this document as a list of (Christian) Passover dates, and can be dated precisely as starting in 725 ce; this provides an approximate date for the text’s composition. Palestinian provenance is most likely. Some of the Easter cycle’s features have been Judaized, seemingly to adapt it for Jewish use. This text opens a new perspective on transfer of knowledge from Christians to Jews in this period, and also provides a context for the origins of the fixed Jewish calendar. Edition of this manuscript has been assisted by multispectral imaging (MSI).