A month is first divided into four weeks, and seven days is a week.

In the process of gazing at the starry sky and looking at the air, the ancients found that the sky was round and the earth was square, and there were three places and four places. At the same time, they take this multiple of three and four as the resonance number between heaven and earth, 12, 24.36.72, and apply it to various places, such as 12 months a year, 12 meridians in the human body, and 24 solar terms a year.

At the same time, the principle of five elements and four images is also used more. The 360 days in a year are divided into 12 months, which are four seasons, namely, spring, summer, autumn and winter, with three months in each quarter and four weeks in each month. At the same time, according to the four images, the 28 stars are divided into four groups, with seven stars in each group, which constitute the four gods of Qinglong, Baihu and Suzaku Xuanwu. So apply this idea to calendar making, a month is divided into four weeks, and a week is seven weeks.

But there is another saying: In 18 BC, King Hammurabi of Babylon unified the two river basins. When he was in office, he formulated a code to safeguard the interests of the slave owners, which was the first relatively complete written code known in history. After the death of Hammurabi, the kingdom of Babylon was in a state of chaos and division for a long time, and was finally destroyed by foreign countries. Babylonians used hexadecimal to calculate time and circumference, which was widely used all over the world. They also formulated the lunar calendar, stipulating that seven days is a week.

So some people say they are ancient Babylonians.