Liturgy of the Hours

By the end of the 5th century, the Liturgy of the Hours was composed of seven offices. Of these seven, Compline seems to have been the last to appear, because the 4th century Apostolic Constitutions VIII iv 34 do not mention it in the exhortation "Offer up your prayers in the morning, at the third hour, the sixth, the ninth, the evening, and at cock-crowing".  An eighth office, Prime, was added by Benedict of Nursia in the 6th century. These eight are known by the following names, which do not reflect the times of the day at which in the second millennium they were traditionally recited, as shown by the use of the word "noon", derived from Latin (hora) nona, to mean midday, not 3 in the afternoon:

• Matins (during the night, at midnight with some); also called Vigils or Nocturns or, in monastic usage, the Night Office
  
  
• Lauds or Dawn Prayer (at Dawn, or 3 a.m.)
  
  
• Prime or Early Morning Prayer (First Hour = approximately 6 a.m.)
  
  
• Terce or Mid-Morning Prayer (Third Hour = approximately 9 a.m.)
  
  
• Sext or Midday Prayer (Sixth Hour = approximately 12 noon)
  
  
• None or Mid-Afternoon Prayer (Ninth Hour = approximately 3 p.m.)
  
  
• Vespers or Evening Prayer ("at the lighting of the lamps", generally at 6 p.m.)
  
  
• Compline or Night Prayer (before retiring, generally at 9 p.m.)

This arrangement of the Liturgy of the Hours is attributed to Saint Benedict. However, it is found in Saint John Cassian's Institutes and Conferences, which describe the monastic practices of the Desert Fathers of Egypt.