The origin of the seven days of the week

The ancient Babylonians were very good at observing things in life. By observing the moon, they discovered that the change of the moon is switching between semi-full moon - full moon - new moon. For the moon: from semi-full moon to full moon, it takes 7 days.

; From the full moon to the semi-full moon, the time is another 7 days.

From the half-full moon to the disappearance, it takes 7 days; from the disappearance to the half-full moon, it takes another 7 days.

7 days is also the cycle of waxing and waning of the moon.

From this, they concluded that 7 days is the cycle of the moon's waxing and waning, so they divided a month into four weeks and set seven days as a cycle, which is our current week.

The ancient Babylonians first used seven days as a time unit for a week. Later, the Jews spread it to ancient Egypt, and from ancient Egypt to Rome. After the 3rd century AD, it spread widely to various European countries.

Extended information: The origin of the Chinese week. The week was called Qiyao in ancient China.

In the Xia, Shang and Zhou dynasties of China, Qiyao refers to the seven main stars including the sun, moon, and five planets. It was an important organizational component of the astronomical phenomena at that time.

Later, it was used as a time unit of seven days per week, so it was called a week.

Qiyao in China was not initially used as a unit of time.