File:Horae ad usum Bituricensem p19.jpeg

English: Pages of the Horae ad usum Bituricensem (Book of hours of Berry) written in the 15th century (see also Très Riches Heures du Duc de Berry for another book of hours of the same region, created and published at the same period, but very richly illuminated later in its most famous version).

• The page on the right side is the first page of extracts of the gospel (written in Medieval Liturgic Latin).
• The page on the left side is the last page of a calendar of Christian saints and feasts (written in Late Old French, with the orthography of the Oïl variant used in the royal domain in Central-Northern France) for year 1427 in the Julian calendar (with years counted from January 1st in France), and shows the second half of December 1427 (days 16 to 31).
• Week days are noted (before names of saints or feasts) by letters from a to g: these letters are relative to the 1st day of the year (a for January 1 falls on Wednesday, like also for December 31 because 1427 was not a leap year, so e falls on Sunday) and do not match with dominical letters (which would be backward from g for Monday to a for Sunday).
• In the right margin beside some days, there are abbreviated annotations for Christian observance (days in the month are not numbered here, but were designated by the Christian saints or feasts).

Ursin in French (Ursinus in Latin), whose feast day in the martyrology of Ado would be the 9th November (in states of the former Germanic Holy Empire), is mentioned here on 30 December (as it was celebrated in France, and notably in Bourges, where Saint Ursin died). The dates of celebration of Christian saints has varied considerably across countries and years, before calendars started to use numbers for the days of the month and consistant names for days of the week (after the adoption of the Gregorian calendar reform starting in 1582).