In order to mark the position of the sun on the ecliptic every month, the Babylonians divided the sky that the sun passes through every month into 12 constellations, that is, the zodiac, and the 12 constellation of the zodiac (that is, the 12 constellation) is Pisces. In ancient China, the Chinese zodiac on Sunday was divided into twelve days and twelve times.

In ancient China, there was a branch of 12 to record the time and sequence, and the sea platoon was 12. 10 trunk and 12 underground branch are recycled, which is a calendar year method in ancient China, with 60 years as a cycle. Each earthly branch is matched with 12 animals to become the zodiac, and 12 animals are pigs. 1 year is divided into 24 solar terms with 12 earthly branches. The time of day is also represented by local branches, so there are 12 hours in a day, starting from midnight, which is equivalent to 23:00 the day before and 0 1:00 the day before.

The modern international calendar divides 1 year into 12 months. 12 months vary in length, but they all have 12 days.

1 day is divided into 24 hours, with 12 hours in the morning and afternoon respectively. In a day, the hour hand of a clock will turn on the dial twice, divided by 12 hour. The minute hand length is slightly equal to 1.5 times of the hour hand, and the running speed is 12 times of the hour hand.

In addition, in terms of calendar years, there are 12 BC, 12 AD, 12 BC and 12 AD recorded by human beings.