The Liturgy of the Hours is a liturgy of prayers for every day of the year, when prayers are assigned for particular times of each day. Priests, laypeople, and those belonging to Holy Orders are all encouraged to follow the Hours. All the prayers, hymns, psalms, and readings that comprise the Liturgy of the Hours can be found in the Breviary, which is a voluminous compendium of prayers used by the clergy.

The tradition of the Hours goes all the way back to the early days of the Church when monks and priests prayed every morning at sunrise and every evening at sundown, relying on a psalter, or Book of Psalms. The Book of Psalms forms the basis of the Liturgy of Hours. Over the years, prayers, songs, psalms, and meditations were added to the original contents of the psalter.

At first, bishops and choirs chose the psalm that seemed suitable for the occasion. Different psalms might be better suited to morning or evening prayer, or to particular feast days. At one time, monks tried to recite the whole 150 psalms in one day. When this turned out to be too time-consuming, the recitation was spread over a week, each day divided into hours.

In the 1960s, Vatican II revised and formalized the system of prayers, and the Liturgy of the Hours became known as “Divine Office.” Now, once a year, Catholics can get a published work with the prayer structure formalized and laid out — with special psalms for particular feast and saints' days — so that all Catholics can worship in the same way.

In a single day, the Divine Office consists of Lauds and Vespers for morning; Matins, a prayer that may be recited at any point during the day; Terce, Sext, and None, prayers for midmorning, noon, and midafternoon; and Compline, which is the night prayer. In cathedrals and monasteries, Mass is celebrated after the Terce (which is said at the “third hour,” or 9 A.M.).