Medium: Ink and pigments on vellum
For the medieval thinker, time was a subject with a great deal of potential. Time was tied into the divine order of everything, making what may seem an heretical or pagan subject such as astrology actually perfectly alright. Medieval calendars were founded on the idea that the celebration of Easter was a kind of cosmological time fix and was related to the positions of the sun and moon (which were among the planets orbiting the earth). Calendars had a place in church service books and prayer books where they served as a kind of diary to keep track of feast and saints' days, but also they would be included in scientific and astrological books along with complex diagrams showing relationships and harmonies of the elements of creation. This calendar belonged to the priory of Christ Church cathedral, Canterbury.
This page has the beginning of prayers for the first Sunday in Advent. Opening with the blessing, the prayers would have been said by the community as part of their daily prayers and would change with the seasons. A calendar and other material on the lengths of months and days would have been necessary to determine which prayers were the correct ones and when to say them. The shrunken and darkened appearance of the page is due to its having been nearly destroyed in the Cotton library fire of 1731.