 The Rule of St. Columbanus and the Bangor book distinguish eight Hours;


At the four lesser Hours St. Columanus orders three psalms each; at Vespers, "ad initium noctis", and "ad medium noctis" twelve each, and "ad matutinam", a very curious and intricate arrangement of psalmody varying in length with the longer and shorter nights.On Saturdays and Sundays from 1 November to 25 March, seventy-five psalms were recited on each day, under one antiphon for every three psalms.From 25 March to 24 June these were diminished by three psalms weekly to a minimum of thirty-six psalms.