The apparent diameter of the sun (the angle between the two sides of the sun and the eyes) is about 32 minutes (a little more than half a degree), and it takes 24 hours for the sun to survey the sky once (360 degrees), so the time to move for 32 minutes is the time when the sun grows from its long outcrop to the horizon. Mathematical calculation is relatively simple, so I won't say much here. In addition, because the distance between the sun and the earth is not fixed, the apparent diameter of the sun will change accordingly, so the score of 2. 1 can only be an approximate number, and summer is shorter than winter.