Unit of time

It refers to the time, ancient times a talent 12 hours, the use of the earth branch as the name of the hour, and the ancient custom called. The hour starts at midnight. Gu yanwu "day knowledge record" : "since the han following. The calendar became increasingly dense, so it was divided into twelve hours in one day. Her (Du Yuankai) midnight that is, the so-called son of today also, ugly and chicken calls, Yin also daylight, sockets and sunrise, the food is also, in the corner have also, noon also between Japan and China, Die not also, feeding time, and also into unitary also, dusk is also of the man hai also. A day is divided into twelve parts, and this is the beginning."
At the beginning of the northern song dynasty, each hour was divided into "chu" and "zheng".