Liturgy of the Hours

The Liturgy of the Hours (Latin: Liturgia Horarum), Divine Office (Latin: Officium Divinum), or Opus Dei ("Work of God") are a set of Catholic prayers comprising the canonical hours, often also referred to as the breviary, of the Latin Church. The Liturgy of the Hours forms the official set of prayers "marking the hours of each day and sanctifying the day with prayer." The term "Liturgy of the Hours" has been retroactively applied to the practices of saying the canonical hours in both the Christian East and West–particularly within the Latin liturgical rites–prior to the Second Vatican Council, and is the official term for the canonical hours promulgated for usage by the Latin Church in 1971. Before 1971, the official form for the Latin Church was the Breviarium Romanum, first published in 1568 with major editions through 1962.

The Liturgy of the Hours, like many other forms of the canonical hours, consists primarily of psalms supplemented by hymns, readings, and other prayers and antiphons prayed at fixed prayer times. Together with the Mass, it constitutes the public prayer of the church. Christians of both Western and Eastern traditions (including the Latin Catholic, Eastern Catholic, Eastern Orthodox, Oriental Orthodox, Assyrian, Lutheran, Anglican, and some other Protestant churches) celebrate the canonical hours in various forms and under various names. The chant or recitation of the Divine Office therefore forms the basis of prayer within the consecrated life, with some of the monastic or mendicant orders producing their own permutations of the Liturgy of the Hours and older Roman Breviary.

Prayer of the Divine Office is an obligation undertaken by priests and deacons intending to become priests, while deacons intending to remain deacons are obliged to recite only a part. The constitutions of religious institutes generally oblige their members to celebrate at least parts and in some cases to do so jointly ("in choir"). Consecrated virgins take the duty to celebrate the liturgy of hours with the rite of consecration. Within the Latin Church, the lay faithful "are encouraged to recite the divine office, either with the priests, or among themselves, or even individually", though there is no obligation for them to do so. The laity may oblige themselves to pray the Liturgy of the Hours or part of it by a personal vow.

The present official form of the entire Liturgy of the Hours of the Roman Rite is that contained in the four-volume Latin-language publication Liturgia Horarum, the first edition of which appeared in 1971. English and other vernacular translations were soon produced and were made official for their territories by the competent episcopal conferences. For Catholics in primarily Commonwealth nations, the three-volume Divine Office, which uses a range of different English Bibles for the readings from Scripture, was published in 1974. The four-volume Liturgy of the Hours, with Scripture readings from the New American Bible, appeared in 1975 with approval from the United States Conference of Catholic Bishops. The 1989 English translation of the Ceremonial of Bishops includes in Part III instructions on the Liturgy of the Hours which the bishop presides, for example the vesper on major solemnities.