The medieval Book of Hours evolved out of the monastic cycle of prayer which divided the day into eight segments, or "hours": Matins, Lauds, Prime, Terce, Sext, Nones, Compline, and Vespers. By the early fifteenth century, the format of the Book of Hours had developed to satisfy the demands of private, as opposed to communal, devotion. These portable books are smaller in format than their monastic forebears, designed for use by individuals, with a liturgical system somewhat less complicated than monastic liturgy and more "user-friendly." A Book of Hours invariably begins with a liturgical calendar, listing feast days in chronological order along with a complicated method of calculating the date of Easter. The seven Penitential Psalms are usually included as well, and additional prayers (devoted to particular saints or personal issues) according to the desires and needs of the owner.
In Books of Hours are preserved some of the finest works of medieval art. Each section of the manuscript traditionally begins with an illuminated miniature that complements the prayers, to stimulate contemplation and meditation in the reader. Because they were expensive and spectacular works of art, the ownership of these manuscripts was limited mainly to royalty, nobility and the very wealthy. They are often adorned with coats of arms, and portraits of patrons may sometimes be found within the miniatures. As their popularity increased, an efficient system of book production and trade developed to match the demand for Books of Hours. Professional scribes produced the texts in one location, the miniatures were painted in artists' workshops, and the two brought together in the bookbinder's hall. Patrons could choose the texts and miniatures they wanted, or purchase complete, generic manuscripts in stationers' book shops. A thriving economy developed around the production of Books of Hours, especially in centers such as Bruges and Utrecht.