The Book of Hours was a ritual object, but it was also a practical one. Owning books at all was a luxury, so it made sense to have a cornerstone of people’s collections be as useful as possible. As such, Books of Hours often contained large amounts of supplementary material to the core prayers, designed to be applicable throughout the book and its user’s lifespan.

At the start of almost every Book of Hours is a calendar. This is not ritualized; while there are saints’ days listed, there aren’t any prayers. It’s a real, hands-on calendar, designed to be used in daily life, even if it’s hard to recognize as such due to the differences between modern calendars and medieval ones. In a Book of Hours calendar, each month is given a list of its days, without days of the week. To figure out what day of the week it is, a seven-letter cycle from A to G is listed next to the days, and each year you figure out which letter means Sunday and go from there. This means that the same book can theoretically be used for as many years as the owner has it. There are also special Roman numerals, called “golden numbers” that help the user to find the date of Easter in any given year. The system to do this is incredibly complicated, but you only have to do it once a year. Lastly, there is a series of symbols representing the old Roman calendar, which counted days relative to a few fixed days each month.

A sparsely decorated calendar page showing the month of May with its saints' days. Note the golden numbers at the far left, the dominical A-G next to it, and the symbols representing the Roman calendar system.

This calendar was useful in many ways to its users, but it can also come in handy when looking at a Book of Hours today. It’s almost always the first thing you see, which lets an observer begin to figure out the sensibilities of the book they’re holding. Is the calendar lavishly decorated, with pictures of the work done during each month and the Zodiac? The book is probably more ornamented too, and designed as a luxury item. Is the calendar pragmatic and simple? The book was probably made to be used, and the owner wouldn’t have had other easier calendars lying around. The handwriting style of the text and the color choice can also inform a reader of the amount of wealth going into a given book, which in turn tells you something about who would have used it.

A more lavishly decorated calendar page showing the month of March. In addition to saints' days and the calendrical information, there is a border on one side with images of flowers and an inlay showing the labor of the month for March, cutting out dead branches and trees.

A continuation of March from the same book. This page shows the Zodiac sign for the month, Aries.

On the larger scale of life, the Office of the Dead was included in almost every Book of Hours, usually after the Litany of Saints. Part of a funeral service, the text a reader would see in their own book was the same as what priests would say officiating over a deceased loved one. The inherent emotional power of this kind of prayer motivated images dealing with mortality and loss, with large variation in subject matter and its severity. Depictions of a church funeral service were common, as were taunting figures of skeletons and corpses. Some even focused on non-religious folktales, like The Three Living and the Three Dead, a story in which dead bodies tell healthy young men that “as you are, we were; as we are, you will be”. Readers would be forced to grapple with their own mortality as they dealt with the loss of their loved ones, but through the constant text of their Book of Hours rather than just the messy outside world. In a place like medieval Europe, where death could be around the corner no matter one’s age or health, the Office of the Dead made the Book of Hours into a reminder of the owner’s entire life. This made the book's time-markers into a facet of its religious identity.

The Office of the Dead's illustrations served to ground the funeral liturgy in the real world and remind readers of their own mortality. This could be done through literal depictions, like this image of a dead person having prayers read before them, or through figurative storytelling, like The Three Living and the Three Dead.