Traditional Culture Encyclopedia - Almanac inquiry - How to understand sidereal day and Sun Day? What is the difference?

How to understand sidereal day and Sun Day? What is the difference?

Solar day is the time interval when the sun passes through the same meridian twice in a row.

Sidereal day is the time interval when the meridian points to the same star twice.

First, the number of leap years in normal years is different.

1, sidereal day: there are 366 sidereal day in normal years; There are 367 sidereal day in leap years.

2. Solar days: There are 365 solar days in a normal year; There are 366 solar days in leap years.

Second, the foundation is different.

1, solar day is defined according to the movement of the sun, which can be divided into apparent solar day and peaceful solar day.

2. sidereal day is based on the movement of stars, and sidereal day is the rotation period of the earth.

Extended data:

The earliest and most popular solar day in the history of China is June 19th of the lunar calendar. Rizhao has the custom of celebrating the solar festival, offering sacrifices to the sun god and celebrating the birthday of the sun.

In China's lunar calendar, only June 19 is the Sun Day (that is, the birthday of the sun) and the enlightenment day of the Bodhisattva. The sun worship custom in Rizhao area is the Tiantai Mountain Lower Sun Festival (Old Mother Temple Fair) with the longest history, the largest scale and the most extensive influence.

Baidu encyclopedia-sun day

Baidu Encyclopedia-sidereal day