The Hours are four relatively brief prayer services of the Daily Cycle that mark the various principal hours of the day. First Hour corresponds to daybreak (6:00 a.m.). Third Hour corresponds to mid-morning (9:00 a.m.) Sixth Hour corresponds to mid-day (12:00 noon) Ninth Hour corresponds to mid-afternoon (3:00 p.m.) These services, together with the other services of the Daily Cycle, are usually contained in a bound collection called the Book of Hours, also known as the Horologion (Greek) or Chasoslov (Slavonic). (Source: orthodox wiki.org)