The Day Unit in Antiquity and the Middle Ages


March 1, 2018- August 1, 2018



Jonathan Ben-Dov (University of Haifa)

Sacha Stern (UCL)


This project aims to shed light on a dark corner in history, which has surprisingly been minimally investigated until now: How was it that the unit of “day” and its primary division into 12 “hours” came to be conceived in human culture? The division seems to have been gradually developed in ancient Egypt, and then migrated also to cuneiform sources from Mesopotamia. It then circulated, not quite smoothly, into the Greek world and subsequently into Western late antique and medieval culture. This account remains vague because there has been no comprehensive and solid research that could clarify it more pointedly. 

New concepts of the division of the day required proper technological means to express them. After tracing this historical riddle however, much remains to be explored for subsequent periods in history. We ask how the science and technologies of time measurement determined the structure and division of the day unit, conceptually as well as in practice, and conversely, to what extent did conceptual and practical divisions of the day unit underpin and influence the development of time measurement technologies. Time is in many ways a human construction, which requires a set of rituals and cultural agents in order to reinforce it. We aim to study these various mechanisms.

The suggested team is a unique combination of experts in the history of time in their respective fields. Such a group has never before been assembled to study this type of question. The group consists of historians of science and technology, as well as law and religious and cultural institutions. The historical periods and geographical spread covered by the group is exceptionally wide: from ancient Mesopotamia and Egypt, to ancient Jewish culture (Second Temple, rabbinic) and into Medieval Judaism, Greek and Roman history, Islamic culture, and the literature of medieval Ethiopia.



  • Sarit Kattan Gribbetz, Fordham University
  • Wayne Horowitz, The Hebrew University of Jerusalem
  • Tzvi Langermann, Bar-Ilan University
  • Israel Yuval, The Hebrew University of Jerusalem