The Spring Equinox is the fourth solar term among the twenty-four solar terms and is an important time for farming.The sun shines directly on the Earth's equator, making day and night almost equal.In ancient times, spring was from the beginning of spring to the beginning of summer, and the vernal equinox was in the middle of the three months of spring.The sun reaches 0 degrees ecliptic longitude, which is celebrated every year from March 19th to 22nd in the Gregorian calendar.% At the vernal equinox, yin and yang are half in phase.Therefore, the day and night are even and the cold and heat are equal.