12 hour is equivalent to 24 hours and 2 hours per hour. 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. Twelve o'clock was created by the ancient working people in China according to the natural laws of the sun, the changes of the sky and the daily production activities and living habits.
Twelve hours: Zi, Ugly, Yin, Mao, Chen, Si, Noon, Wei, Shen, You, Xu, Hai, two hours is one hour. Twelve o'clock system was adopted 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. It is also expressed by the twelve earthly branches, and it is the child time from 23: 00 to 1 at midnight, the ugly time from 1 to 3: 00, and the Yin Shi time from 3: 00 to 5: 00, which are recursive in turn.
The 24-hour system has many advantages over the 12-hour system.
1, not confusing
The 24-hour clock will not confuse morning time and afternoon time. In the 12 hour system, 7 o'clock can refer to either morning or afternoon. In a calendar or similar document, you can tell at a glance whether it is morning or afternoon. This is especially important for organizations that need to operate 24 hours a day, such as airlines, railway timetables and the military.
2, accurate description
Can accurately describe the time of day. For example, it is difficult to determine whether it is "00:00 on February 3" or "00:00 on February 4", that is, "24:00 on February 3". The 24-hour clock can be easily arranged in character and time order without using additional codes to correct the order.