Our ancient ancestors divided a day and night into twelve periods, and each period was called an hour. Twelve o'clock can refer to either a day or any time. Twelve o'clock is an original creation created by our ancient ancestors according to the natural law of the appearance and appearance of the sun in a day, the change of the sky and their daily production activities and living habits. It was used in the Western Zhou Dynasty. In the Han Dynasty, it was named Midnight, Cockcrow, Pingdan, Sunrise, Food Time, Horn, Japan-China, Sundial, Sunset, Dusk and Rending, and it was also expressed by twelve earthly branches. Details are as follows:

1, child time: 23: 00-1:00;

2. Ugly time:1:00-3: 00;

3. Yin Shi: 3: 00 to 5: 00;

4. Shi Mao: 5: 00 to 7: 00;

5. Daily time: 7: 00-9: 00;

6. Sixi: 9: 00-11:00;

7. At noon:11:00-13: 00;

8. Out of date:13: 00-15: 00;

9. Xinshi:15: 00-17: 00;

10, unitary time:17: 00-19: 00;

1 1, Kistler:19: 00-21:00;

12, Shihai: 21:00-23: 00;