Those who crow in the middle of the night are ugly, those who crow in the air are ugly, those who rise in the dark, those who eat in the morning are in the corner, those who eat at noon are in the afternoon, those who lose during the day are not in the morning, those who eat in the morning are in the evening, and those who settle in the sea.

The ancient working people 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. 12 hour is equivalent to 24 hours and 2 hours per hour.

This is the twelve-hour system used in the Western Zhou Dynasty. In the Han Dynasty, it was named Midnight, Crow, Pingdan, Sunrise, Food Time, Horn, Japan-China, Sundial, Sunset, Dusk and Man's Decision. Also represented by the twelve earthly branches.

The time corresponding to twelve o'clock is: midnight 23 ~ 1 o'clock, clown time 1 ~ 3 o'clock, Yin Shi time 3 ~ 5 o'clock, Shi Mao time 5 ~ 7 o'clock, morning time 7 ~ 9 o'clock and noon 9 ~1o'clock. Joint time 17 ~ 19, Chu time 19 ~ 2 1 point, sea time 2 1 ~ 23.