What does Sun Day mean?

Solar Day has two concepts. One is the concept of folklore, which refers to the birthday of the sun. It's June 19th of the lunar calendar, which is recorded in the Yellow Calendar. Second, it refers to the "Japanese Obsidian Day" in China's ancient "Seven Obsidian Days", which coincides with the western Sunday.

Sun Day, the predecessor of Sunday, has been designated as a rest day in ancient Rome, and people engage in worship activities without working. Latin, di solis. Sunday refers to the day after Saturday and before next Monday. The Latin name of Sunday is Di Souris, which means Sun Day. French is dimanche, which comes from the Latin word meaning "the day of the Lord"; English is Sun Day, which comes from Sunday. Russian is вокресенье, which means "Sunday".

Calculation method of solar day

A solar day is equivalent to a day and night of the earth, that is, a day and a night. Of course, the solar day mentioned here does not mean that the earth really rotates once, but the time interval when the sun passes through the same place, such as the meridian plane of the earth, and the earth rotates and revolves at the same time.

It takes about 23 hours, 56 minutes and 4 seconds for the earth to rotate once, and 3 minutes and 56 seconds for revolution, so the total time for rotation and revolution is exactly 24 hours. The time when the earth rotates is called sidereal day. Sidereal day and Sun Day are different. Simply put, the difference between them is about 4 minutes, and the solar day is slightly longer than that in sidereal day.