In the practice of Christianity, canonical hours mark the divisions of the day in terms of periods of fixed prayer at regular intervals. A Book of Hours normally contains a version of, or selection from, such prayers.

The practice of daily prayers grew from the Jewish practice of reciting prayers at set times of the day: for example, in the Book of Acts, Peter and John visit the temple for the afternoon prayers (Acts 3:1). Psalm 119:164 states: "Seven times a day I praise you for your righteous laws" which is among the scriptural quotes in the attestation of Saint Symeon of Thessaloniki that commences "The times of prayer and the services are seven in number, like the number of gifts of the Spirit, since the holy prayers are from the Spirit."