Analysis: It is known that July 1 is a Sunday with seven days in a week, so the formula 31-1= 30,30/7 = 4 ... 2 is available, so the two days after Sunday are Tuesday.

The origin of the week:

Zhou originated in Babylon as a time period. The world-wide seven-day week system was first formulated by the Roman emperor Constantine the Great, who officially declared seven days as a week on March 7th, 32 1 year, and this system has been in use ever since. In China, when Christianity spread in China in the late Ming and early Qing Dynasties, Zhou gradually became known. After the use of the Gregorian calendar was stipulated in the Republic of China, the week gradually became popular.

Zhou is called the Seven Obsidian in China. During the Xia, Shang and Zhou Dynasties in China, Seven Obsidian refers to the seven main stars, such as the sun, the moon and the five planets, which was an important part of astronomical astrology at that time. China's seven obsidians did not begin as a unit of time. In the west, the ancient Babylonians first used seven days as 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 European countries. ?