The chronography of Annianus, composed in 412, stands out by closely mapping the chronology of the world onto the Alexandrian 532-year Easter cycle, of which he may be the originator. He also defended that Christ was born in AM 5500, which had its roots in Christian exegesis. This generated a set of chronological anomalies, especially the fact that he situated birth and death of Christ about 10 years later than usual in Christian chronography. As a consequence, there is hardly any trace of Annianus before the second half of the sixth century, when Justinian’s attempt to impose the Christmas date of 25 December on the church of Jerusalem sparked a controversy. Annianus’ chronology, which supported the date of 25 December, was put forward by the defenders of that date (especially Heron), whilst those defending 6 January drew on Andreas. Due to this controversy, Annianus’ chronography travelled from Alexandria to Constantinople and was transmitted to Syriac and hence into Arabic.

Andreas composed an Easter table and 200-year list of Easter dates that started in 352. It was based on the work of Anatolius of Laodicea and Hippolytus. To this a chronography was added, which is attested in Syriac but mostly in Armenian. Indeed, at the end of the sixth century, the work of Andreas travelled to Armenia, where it became the basis for the Armenian calendar. Andreas is the first known author to combine computus and chronography. He is also the earliest author to defend 6 January as the date for Christmas, and he is unique in proposing AM 5600 as the start of the Christian era.

Between a hundred and two hundred manuscripts connected with Brittany, written in the ninth and tenth centuries, can be identified by their script, contents and Old Breton glosses; they survived the Viking age by being taken to Francia or England, and open a window on the sources and external contacts of Bretons’ scholarly culture. The manuscripts contain a wide variety of Latin texts, biblical, legal, grammatical, technical and historical. One of the most important subsets consists of manuscripts of the Irish canon law compilation, Collectio Canonum Hibernensis: it is unclear whether the text was obtained from Ireland or via Irish-influenced centres on the Continent, but the ability of Breton scribes to access both the extant versions in full, together with some of their source-texts, implies contact with the milieu of the original compilers. Glosses show that even texts that were widely available on the Continent, like grammars and the scientific writings of Bede, reached Bretons through Irish contacts. Some manuscripts reveal collaboration between annotators writing in Irish, Welsh and Breton, providing a context for the sharing of hagiographical information discussed in the previous chapter. The occasional sharing of rare texts allows us to pinpoint a few centres where such encounters may have taken place, among them are Reichenau and Echternach. The survival of Breton manuscripts in England suggests that Breton scholarship played a considerable part in the reconstruction of the English Church in the tenth century, after the Viking age.

This chapter begins with an account of the roles of Charlemagne and Alcuin in supporting the study of computus and astronomy in the Carolingian Empire. It then offers an outline of the expanded astronomical and meteorological information found in Carolingian ‘encyclopedias’ of computus. A key problem for users of these collections was the lack of accurate astronomical observations and calculations, which enforced continuing dependence on lists of short-term ‘signs’ of coming weather, mostly derived from Pliny. One attempt to improve the range of knowledge available took the form of beautifully illuminated versions of Aratus’ long poem, in volumes known as Aratea. The dissemination of this body of information is traced through analyses of surviving manuscripts, which demonstrate the resources being devoted to the subject across mainland Europe. Separate consideration is given to Anglo-Saxon England, where Viking conquests and wars had caused serious disruption, and where the teaching of Abbo of Fleury, and his pupil Byrhtferth, was crucial. The chapter argues that possession of superior astronomical and meteorological knowledge was highly vaued by rulers in both secular and spiritual spheres.

This chapter first explores how early medieval writers, and especially Isidore and Bede, made fundamental contributions to a new understanding of the natural world and its workings. They both quarried classical works for factual information and empirical observations, and placed these within a Christian cosmological model. An outline is given of the monastic science of ‘computus’, which was fundamental for teaching on natural philosophy and for theories about the weather in particular. Summaries of introductory works by both Isidore and Bede demonstrate their respective meteorological models; Bede’s views on the powers of the planets are covered in detail. Special attention is given to Bede’s The Reckoning of Time and the complex information on astronomy and meteorology which it expounds. An important conclusion is that Bede produced an understanding of weather as the intelligible and predictable result of astronomical and climatic factors. Overall, the chapter argues that classically derived natural philosophy and Christian cosmology were successfully integrated, and that the two together provided the basis for a new approach to weather and its prediction.