At that time, the sun shadow was measured during the day, and the time was measured by dripping water from a clepsydra at night. But this is not the earliest time measurement method.
Before this, the ancients counted a day according to the rise and fall of the sun and the activities of human beings and animals, which was divided into twelve periods: crow, delicious food, sunrise, food time, horn, day, sundial, food time, day, dusk, people decide and midnight.
Due to different seasons, the specific time difference actually reached two hours. Because it is not very scientific, it was finally changed to 12 earth branch timing method.
In addition, in ancient times, there was a method called "changing the clock", which divided the night into five classes: 19 to 2 1 1, 2 1 2 to 23: 00, 23: 00 to 1 3: 00.