UCL Hebrew & Jewish Studies


Saadya Gaon’s Works on the Jewish Calendar: Near Eastern Sources and Transmission to the West

fragment of a page from Saadya Gaon’s works on the Jewish calendar

Saadya Gaon’s Works on the Jewish Calendar: Near Eastern Sources and Transmission to the West (2021–2023) is headed by Prof. Sacha Stern and Prof. Ronny Vollandt (LMU Munich), with Dr. Nadia Vidro as a Senior Research Fellow and is funded by the Fritz Thyssen Foundation.

In the first half of the 10th century, the Jewish calendar had become a major issue for Near Eastern Jewish communities. Calendar controversies broke out among Rabbanites and between Rabbanites, Qaraites and other Jewish movements. The intensity of 10th-century calendar debates was an outcome of the major changes that had occurred through the 9th century, with the institution of a new calendar based on calculation which was widely followed by the Rabbanites by the beginning of the 10th century. These debates were not just about the technical question of how to set the months and years but were fights for legitimacy, authority, and legal independence. It is therefore hardly surprising that the calendar was of great interest to Saadya Gaon, a preeminent scholar and communal leader of rabbinic Babylonian Jewry in the first half of the 10th century.

Saadya b. Joseph al-Fayyumi, better known as Saadya Gaon (882–942 CE), was the most important and influential scholar of Judaeo-Arabic culture in the 10th century. The head of the rabbinic academy of Sura, a polemicist and a polymath, Saadya produced a vast body of writings that had a lasting impact on Jewish literature and culture. His works cover philosophy, liturgy, grammar, Bible translation and exegesis, religious law, and other areas of intellectual activity. Saadya composed at least four works on the calendar and the calendar polemics, and possibly some others that are attributed to him in 10th-century Jewish and Muslim sources but appear lost. Yet Saadya’s works on the calendar and his role in the development of the Jewish calendar literature have not received much scholarly attention.

This project investigates Saadya Gaon’s literary production on the calendar by reconstructing and editing the full corpus of Saadyanic calendar writings, and analysing this corpus against the background of earlier calendar literature and the diffusion of the Rabbanite calendar in later medieval Europe. We will produce critical text editions of Saadya’s works with English translations. Based on these editions, we will study Saadya’s contribution to the development of calendar theory, and the role of his works in fomenting or resolving Near Eastern communal conflicts over the calendar and in the diffusion of the calculated Jewish calendar to the West. We will also reflect on the role and impact of the sciences (astronomy) and of biblical and Talmudic exegesis on Saadya’s calendar theory.

Image: Cambridge University Library, Taylor-Schechter Genizah Research UnitT-S 10K2, folio 1r.

Associated Publications

Nadia Vidro (2023) ‘A lost work or a lost title? Iqāma al-ʿIbbur: T-S 10G5.7, Taylor-Schechter Genizah Research Unit, Cambridge University Library, Fragment of the Month, August 2023

  • A short piece on an elusive calendar treatise by Saadya Gaon, known in research literature as Iqāma al-ʿIbbur.

Nadia Vidro (2023) ‘One Letter at a Time: Reconstructing Saadya's Refutation of Ibn Sāqawayh, Genizah Fragments: Blog of the Genizah Research Unit (13 July 2023)

  • A short piece on working together with the Cambridge University Library Conservation Department to improve the legibility of a crucial but very poorly preserved fragment of Saadya Gaon's polemical treatise Refutation of Ibn Sāqawayh

Nadia Vidro (2022), Saadya Gaon’s Refutation of Anan or a Qaraite Book of Commandments? T-S Ar.21.156, T-S Ar.48.216 and T-S NS 303.1, Taylor-Schechter Genizah Research Unit, Cambridge University Library, Fragment of the Month, May 2022. 

  • A short piece arguing that manuscripts previously identified as a work by Saadya Gaon are, in fact, fragments of a Qaraite legal code.

Q&A Wednesday: Saadiah Gaon and the calendar, with Nadia Vidro

  • A Q&A about the project on the blog of the Taylor-Schechter Genizah Research Unit

Workshops and Conference Panels


Saadya Gaon in the Qaraite literature of the 10th–11th centuries

November 2023, Ludwig Maximilian University of Munich

Saadya Gaon’s anti-Qaraite polemic was fundamental for the development of Qaraite literature. In their turn, Qaraites quoted Saadya and discussed his views so much that their treatises can now be used to reconstruct Saadya’s lost works. This workshop explored anew the inextricable connection between Saadya and the Qaraites by looking at a wide range of previously little studied Qaraite sources from the 10th-11th centuries. The workshop was organised by Ronny Vollandt (LMU), Nadia Vidro (UCL) and Sacha Stern (UCL) and attracted an audience of about 20 participants. Full workshop programme here.


Saadya Gaon between Science and Tradition: Texts, Sources and Impact

December 2022, 54th Annual Conference of the Association for Jewish Studies, Boston

This panel explored Saadya Gaon’s writings on the interrelated subjects of the Oral Torah, the anti-Qaraite polemic and calendar. Papers in the session asked questions such as: How does Saadya’s take on science vs. tradition fit into the context of earlier and contemporary Near Eastern literature? How deep was Saadya’s knowledge of the Rabbanite calendar calculation? What was the nature of Saadya’s calendar writings – were they scientific, polemical or halakhic works? What impact did Saadya’s views have on his immediate successors in the mid- to late-tenth century?


  • Marc Herman (York University), “The earliest reception of Saadia Gaon’s approach to the Oral Torah”
  • Sacha Stern (UCL), “Polemics, halakhah, and science: Saadya Gaon’s understanding of the science of calendar computation” 
  • Nadia Vidro (UCL), “Anti-Qaraite works of Saadya Gaon: a re-evaluation”
  • Respondent: Eve Krakowski (Princeton)

Associated Videos

YouTube Widget Placeholderhttps://youtu.be/wJyCQCWGD08



Nadia Vidro, Saadya Gaon's works on the Jewish calendar. 

A presentation of the project, delivered as part of the Institute of Jewish Studies Autumn 2021 Lecture Series (9 December 2021)