Liturgy of the Hours
In the Catholic Church, the laity are encouraged to pray daily the canonical hours contained in the Liturgy of the Hours, which are done at seven fixed prayer times. Clergy and religious are obligated to pray the Daily Office. Sources commonly used to pray the Liturgy of the Hours include the full four volume set of "The Liturgy of the Hours", the one volume "Christian Prayer" book, and various apps on mobile devices.