BC or AD?
We know that the Psalmist says, “Seven times a day do I praise you.” (Ps. 119:164) We have no idea when those hours were, but we know that from the time of King David or before, good Orthodox Jews were interrupting their normal day at least seven times to stop and do fixed prayers–prayers of praise, prayers of thanksgiving, prayers of adulation. They were not prayers of petition. They are prayers in which the creature approaches the Creator and says, “How privileged I am to be able to come before you, my Lord.”
That’s what fixed-hour prayer is. We know that it was done seven times a day. We just don’t know in ancient Judaism when those hours were. We know, for instance, that in one of the Psalms, King David says, “I rise at midnight to praise you.” Aha! The hour is called lauds, and in the Roman tradition it becomes the prayer of lauds, the prayer at midnight, the prayer of praise.