Diagram of the months, in Isidore, 'De natura rerum'
Medium: Ink and pigments on vellum
The scribes of Anglo-Saxon England copied books on scientific as well as religious subjects in the expansion of learning that had begun under Alfred the Great and continued, fed by increasing contacts with the continent, through the 10th and 11th centuries. This is a copy of one of the most well-known scientific books of the day, 'On the nature of things', on physical science, by Isidore, bishop of Seville, who lived in the late 6th and early 7th century. Written in an elegant script (style of handwriting) which was based on Carolingian styles, the small book is illustrated with diagrams labelled with capital letters in a style that looks back to types of Roman handwriting.
Most medieval copies of 'On the nature of things' include diagrams of some kind. This diagram shows the months of the year and their positions in the calendar. Isidore says, at the bottom of the page, that the year has 360 days: each month has thirty, as in the diagram.