1, the vernal equinox is from March 20th (or 2 1) to April 4th (or 5th) every year. The vernal equinox is one of the solar terms reflecting the changes of the four seasons. In ancient China, beginning of spring, Changxia, beginning of autumn and beginning of winter were used to indicate the beginning of the four seasons. The vernal equinox, summer solstice, autumn equinox and winter solstice are in the middle of each season. On the vernal equinox, the sun shines directly on the equator, and the time between day and night is equal all over the earth. Therefore, the ancient vernal equinox and autumnal equinox are also called "equinox", and there is a folk proverb that "vernal equinox and autumnal equinox are equally divided day and night".

2. Distribute day and night equally. On the vernal equinox, the sun shines directly at the equator, almost as long as the day and night in the world, that is, 12 hour.

3. Divide the seasons equally. If the period from the beginning of spring to the long summer is regarded as spring, the vernal equinox is the midpoint of spring, which just divides spring equally. It takes 90 days to travel from beginning of spring to Changchun, and the vernal equinox is divided into two, hence the name vernal equinox.