Long before there were monasteries, the first Christians kept the Jewish habit of praying at fixed hours. The Psalms were their prayer book; the day had its appointed times to turn to God. As monastic communities formed, they gave this rhythm a fuller shape — a round of prayer that ran from before dawn to nightfall.
The Liturgy of the Hours — also called the Divine Office — is built largely from the Psalms, supplemented by Scripture readings, the canticles of the New Testament, and prayer. To pray it is to let the day be measured not by tasks but by the praise of God: morning and evening, and the hours between.
It is prayed across the traditions — by Roman Catholic, Eastern Orthodox, Anglican, and Lutheran communities, and increasingly by lay Christians of many backgrounds. Its logic is simple and ancient: the day belongs to God, and prayer marks it as his.