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This article surveys the historical points of intersection between the study of chronology and the polemical encounter with Judaism in medieval Latin Christendom. Particular attention will be paid to the work of Roger Bacon, who viewed chronology as a tool that could furnish proof for Christianity, e.g., by supporting a Christological interpretation of the prophecies in the book of Daniel. A second focus will be on the reception and study of the Jewish calendar among Christian scholars and how it both influenced exegetical thought about the chronology of the Last Supper and informed efforts to improve the ecclesiastical calendar. With regard to the latter, it will be argued that the competition with Judaism and the Jewish calendar was an important motivating factor in the debates that led to the Gregorian calendar reform of 1582.

In: Medieval Encounters

A frequently overlooked aspect of the knowledge transfer from Arabic into Latin in the twelfth century is the introduction of the Islamo-Arabic calendar, which confronted Western computists with a radically different scheme of lunar reckoning that was in some ways superior to the 19-year lunar cycle of the Roman Church. One of the earliest sources to properly discuss this new system and compare it to the old one is the anonymous Collatio Compoti Romani et Arabici, found in a manuscript from Tewkesbury Abbey, Gloucestershire. This article contains the first edition and translation of this previously unknown text, preceded by an analysis of its content and sources. As will be argued, the text was written in the second quarter of the twelfth century as a reaction to the astronomical tables of al-Khwārizmī, recently translated by Adelard of Bath, as well as to eclipse observations that had exposed the flaws of the ‘Roman’ computation.

In: Early Science and Medicine

Among the works by Jean des Murs that have yet to be printed are his Canones tabularum Alfonsii, which he wrote in 1339 during his last attested stay at the Collège de Sorbonne. One element of particular interest in this concisely worded text is Jean’s discussion of the length of the solar year, which was the first to take into consideration the consequences of the Alfonsine precession model for the length of the tropical year. Another is his approach to finding the time of true syzygy, which can be compared with some of his earlier writings on the same topic. Taken together, these writings reveal something about Jean’s development as an astronomer over time, as he adjusted his preferred method of syzygy computation in reaction to empirical data. The article concludes with a look at the chapters devoted to the calculation of eclipse times and magnitudes, which turn out to be strongly influenced by John of Genoa’s Canones eclipsium, written in 1332.

In: Erudition and the Republic of Letters


The article introduces and explores a new source on Christian hostility towards Jews during the late Middle Ages. It comes in the shape of a commentary on a Computus Judaicus, which was used as a quadrivial school text in Central and Eastern Europe during the fourteenth and fifteenth centuries. Based on an examination of the rich manuscript tradition, it will be demonstrated how the text contributed to the evolution of the trope of Jewish male menstruation, which is here tied, in a unique manner, to an exposition of the Jewish calendar as a method of lunar reckoning.

In: European Journal of Jewish Studies

This article is dedicated to the obscure Computus of Magister Cunestabulus (England, 1175), which offers a unique spotlight on the way the twelfth-century ‘Renaissance’ in mathematical astronomy impacted the Latin computistical tradition. Armed with an unusually broad array of sources newly translated from Arabic, among them Ptolemy’s Almagest, Cunestabulus applied his advanced knowledge in the service of traditional Latin learning and established Church doctrine, defending the non-existence of Antipodeans in the southern hemisphere as well as the astronomical foundations of the ecclesiastical computus. His intricate explanation of the error underlying the Julian calendar, which was based on the Arabic theory of the ‘access and recess of the eighth sphere’, makes for a technically sophisticated and conceptually intriguing case of Graeco-Arabic science being used for apologetic ends in twelfth-century Latin writing.

In: Early Science and Medicine
A Study with Five Editions and Translations
During the later Middle Ages (twelfth to fifteenth centuries), the study of chronology, astronomy, and scriptural exegesis among Christian scholars gave rise to Latin treatises that dealt specifically with the Jewish calendar and its adaptation to Christian purposes. In Medieval Latin Christian Texts on the Jewish Calendar C. Philipp E. Nothaft offers the first assessment of this phenomenon in the form of critical editions, English translations, and in-depth studies of five key texts, which together shed fascinating new light on the avenues of intellectual exchange between medieval Jews and Christians.
The Life of Jesus and the Emergence of Scientific Chronology (200–1600)
The beginnings of scientific chronology are usually associated with the work of the great Renaissance philologist Joseph Scaliger (1540–1609), but this perspective is challenged by the existence of a vivid pre-modern computistical tradition, in which technical chronological questions, especially regarding the life of Jesus, played an essential role. Christian scholars such as Roger Bacon made innovative breakthroughs in the field of historical dating by applying astronomical calculations, critical exegesis, and the study of the Jewish calendar to chronological problems. Drawing on a wide selection of sources that range from late antiquity to 1600, this book uses the history of the date of Christ’s Passion to shed new light on the medieval contribution to science and scholarship.
In: Time, Astronomy, and Calendars in the Jewish Tradition 
In: For the Sake of Learning
In: Medieval Latin Christian Texts on the Jewish Calendar