Morgan MS M.1093, f. 8
Medieval calendar pages look rather complicated to the modern eye. Typically they are laid our in four columns. In the far right appear the special feasts for each day of the month. These are mostly commemorations of the day the saints were martyred (their “birthdays” into heaven). Other feasts commemorate important events in the lives of Christ and the Virgin. In this example, three colors are used, red, blue, and gold. Ordinary feast days are written in alternating red and blue and special feast days are written in gold. Here, the gold letters used for the Translation of St. Sauveur on August 6 reminds the owner that this is a special day—the Church of St.-Sauveur in Rouen celebrated the deposit of his relics there on that date. It is common for calendars in French Books of Hours to be written in easy-to-read French, as occurs here.
The three columns on the left include, from left to right: the Golden Numbers (from I to XIX), the Dominical Letters (running from A through G), and Kalends, and Ides, and Nones. The Golden Numbers indicate the appearance of new moons and full moons throughout the year. The Dominical Letters help find Sundays and all the other days of the week throughout the year. This esoteric information was extremely important to the medieval Christian, since it helped determine the date of Easter, the Church's most important feast, in any given year. The third column conforms to the Roman calendrical system by which each month had three fixed points (although in this calendar, as was typical for late Horae, the numerals are lacking, making this Roman calendar difficult to use).