The Ordered Universe project now hosts a new resource, an edition and translation (with apparatus) of the Compotus ecclesiasticus by the late Jennifer Moreton, together with an introductory essay by Philipp Nothaff (All Souls College, University of Oxford). The Compotus ecclesiasticus is an early thirteenth century example of the medieval treatises on time and calendrical calculation, and the myriad of other subjects that medieval authors touched on in such studies. As Philipp’s introduction points out computus, the science of time, was an essential element in the organisation of Christian life and its religious ordering. The calculation of Easter and the setting out of the ecclesiastical calendar made computistical knowledge sought after, necessary, and argued over throughout the Middle Ages. For a comprehensive overview see Nothaff, Dating the Passion: the Life of Jesus and the Emergence of Scientific Chronology (200-1600), Brill, 2012.
Works of computus inhabited an encyclopaedic space, often consisting of compendia of knowledge on time, applied mathematics, the body of the universe, human history, medicine and theological reflection. One such, which the Ordered Universe team has been examining is the manuscript known now as Durham Cathedral Library Hunter 100 (more on that soon). Since the motions of the sun and moon lay at the heart of computus, changes in astronomy had significant effects on computus treatises. Western computistical learning responded, in this way, to new translations of ancient and medieval Islamic works on the subject from the later eleventh century. The twelfth century in particular witnessed a flourishing of the genre with a series of collections putting forward different emphases on how time was to be calculated, honouring and questioning earlier authorities, such as Bede, as well as those of more recent acquaintance.
Within these twelfth century developments individuals and communities in the west of England 
bounded by the River Severn and the River Wye made notable contributions. From Walcher, Prior of Malvern active in the first half of the century to Roger of Hereford in the second, scholars of this region showed particular interest in astronomy, astrology and computus. It was here, at Hereford, at the end of the twelfth century, that Grosseteste enters the historical record with some certainty, as a master within the household of Bishop William de Vere. The writings of Simon du Fresne, in praise of liberal arts, as well as those of Roger of Hereford, are an important background to Grosseteste’s own exploration of the mathematical arts, natural phenomena, and computus.
While the Compotus ecclesiasticus was not, as Moreton convincingly showed, from Grosseteste’s pen, the text known as the Comptus Correctorius was (ed. R. Steele, Opera hactenus inedita Rogeri Baconis (Oxford 1909–40), 6. 212–67). As Nothaff”s introductory sets out, so expert was Grosseteste in this field (and those who know the mathematical cast of his mind will find this no surprise at all), that later scribes attributed the Compotus ecclesiasticus to the Lincolnite. The proper identification of a number of treatise identified in the medieval period, and by modern commentators (from Thomson to Southern), was in large part the work of Moreton, until her, premature, death in 2005.
The text available here is the product of careful editing by Immo Warntjes, Charles Burnett and Philipp Nothaff, who decided that it would be best to publish Moreton’s research online. A new edition of the Compotus ecclesiasticus is being prepared by Alfred Lohr, but Moreton’s version stands not only for the interim, but as a substantial resource in its own right. The translation, as well as the edition, makes available and accessible an exemplary text for the genre to a wider audience. This will be a valuable teaching aid, as well as a treasure-trove for those interested in the intricacies of medieval learning. It is interesting, for example, to compare to the much fuller presentation of an earlier computus collection, St John’s College, Oxford, MS 17, by Faith Wallis, The Calendar and the Cloister. It is down to Faith’s encouragement too, that the Compotus ecclesiasticus, comes to be hosted by the Ordered Universe. We hope that it will be used and enjoyed, as well as helping to construct a little more about Grosseteste’s educational and intellectual environment in his formative scholarly years.