noon
All work is done by three relays of artisans ; the first set working from noon till evening , the next from evening till morning , and the third from morning to noon . The Martial day , which consists of about twenty-four hours forty minutes of our time , is divided in a somewhat peculiar manner . The two-hour periods , of which `` mean '' sunrise and sunset are severally the middle points , are respectively called the morning and evening _ zydau _ . Two periods of the same length before and after noon and midnight are distinguished as the first and second dark , the first and second mid-day zyda . There remain four intervals of three hours each , popularly described as the sleeping , waking , after-sunrise , and fore-sunset zyda respectively . This is the popular reckoning , and that marked upon the instruments which record time for ordinary purposes , and by these the meals and other industrial and domestic epochs are fixed . But for purposes of exact calculation , the day , beginning an hour before mean sunrise , is distributed into twelve periods , or antoi , of a little more than two terrestrial hours each .