The length of daylight in Beijing, Wuhan and Guangzhou in the spring and autumn.

On the day of the Spring and Autumn Equinox, the daytime length in Beijing, Wuhan and Guangzhou is 12 hours. In spring and autumn, the sun shines directly on the equator, and the world is divided equally between day and night. The length of the day in the world is 12 hour.

1. The vernal equinox is one of the 24 solar terms. The vernal equinox is the mid-point of 90 days in spring, usually around March 2 1 every year. The direct point of the sun is on the equator, and the world is divided equally day and night. In the time period, it refers to the position where the sun is located between 0 and 15, that is, from March 20th to April 5th. But in fact, it usually refers to the day when the sun is really at 0 degrees of the yellow meridian: March 20 or March 2 1.

2. Every year around September 23rd, when the sun reaches longitude 180 degrees, it enters the "autumnal equinox" solar term. The autumnal equinox, like the vernal equinox, is the earliest solar term established by the ancients. According to "Spring and Autumn Stories Yin and Yang Incoming", "The autumnal equinox is accompanied by Yin and Yang, so it is cold and hot day and night."