In Ancient China the 24 hours of the day were divided into the following 12 two-hour periods, sometimes called “watches”. They are: Zi 子 (11pm-1am), Chou 丑 (1am-3am) , Yin 寅 (3am-5am), Mou 卯 (5am-7am), Chen 辰 (7am-9am), Si 巳 (9am-11am), Wu 午 (11am-1pm), Wei 未 (1pm-3pm), Shen 申 (3pm-5pm), You 酉 (5pm-7pm), Xu 戌 (7pm-9pm), and Hai 亥 (9pm-11pm).