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Calendars in Antiquity and the Middle Ages


ERC Research Project


Al Biruni, ‘Chronology of the Ancient Nations’

The work known in English as ‘Chronology of the Ancient Nations’ was written in Arabic by the famous astronomer and polymath Abu Rayhan al-Biruni (or al-Bayruni) in the year 1000.

It is a monumental compendium of the calendars and chronological systems of a very wide range of societies and cultures from the late antique Hellenistic world and the ancient and medieval Near East and Central Asia, including pagans, Christians, Muslims, Jews, and Zoroastrians, as well as other religious and ethnic groups. It describes not only the technical, astronomical aspects of their time reckoning methods, but also their very varied festivals and liturgical practices.This remarkable product of early Islamic scholarship sheds light on cultural and religious diversity in the early Islamic world. In the context of this project, it constitutes an important milestone in the standardization of time-reckoning in the medieval world.


Muhammad forbids intercalation

Our researcher in this area is Dr François de Blois.

The ‘Chronology’ was first published, and then translated into English, by Eduard Sachau in 1878 and 1879. Sachau’s edition is based on three late manuscripts, all of which are in fact copied from a common and mediocre archetype, which was not accessible to Sachau, but has since been acquired by the Edinburgh University Library; it was copied in 1307. In this manuscript, substantial portions of the text are missing, e.g. in chapters 6, 7, 8, 9, 16, 20. Chapter 16, in particular, is mostly missing in Sachau’s edition: it concerns the Christian Computus, i.e. the calculation of the date of Easter and of the Passion. These and other deficiencies can now be corrected with the help of superior copies, in particular, a manuscript in Istanbul from the 12th century and two from the 15th century. Moreover, research in the course of the last hundred years has shed considerable light on obscure or misunderstood passages in al-Biruni’s book.

As part of this project, an entirely new edition of the text, with critical apparatus, English translation, and commentary, will be prepared. This new edition will serve as a solid foundation for any future research into Biruni’s ‘Chronology’ and into the chronological systems discussed in that book.

Our main research questions are:

1. Why was Biruni’s ‘Chronology’ written? Was it intended for practical instruction, e.g. to explain how to reckon dates of festivals , or how to date economic and official documents? Or did it serve other purposes, e.g. to polemicize against other religions?

2. Is Biruni’s presentation of calendars descriptive or prescriptive? If prescriptive, what did the ‘Chronology’ contribute to the fixation and standardization of medieval calendars?