Spring equinox and autumn equinox are one of the twenty-four solar terms, the spring equinox is around March 22 every year, referring to the end of winter, and the autumn equinox is around September 22 every year, referring to the slow start of winter. At the spring equinox, the global day and night are equal, after the equinox, the northern hemisphere, the day grows longer and the night grows shorter, the southern hemisphere, the night grows longer and the day grows shorter; at the autumnal equinox, the time of day and night is equal, and by the long day and night gradually shorter day and night, the climate from hot to cool.

The vernal equinox one of the twenty-four solar terms, is the fourth solar term in spring. Doo refers to non, the sun's yellow longitude reaches 0 °, in the annual calendar March 19 ~ 22 cross section. The equinox is important in astronomy, the northern and southern hemispheres day and night, since this day after the direct position of the sun continues to move from the equator to the northern hemisphere, the northern hemisphere day began to be longer than the night. Vernal equinox is also characterized by warm weather, abundant rain and bright sunshine. The vernal equinox is the period of time when the sun is located between 0° and 15° of the yellow meridian, i.e., from the day of the vernal equinox to the day before the Qingming Festival, which is approximately between March 20 and April 5 on the Gregorian calendar. Vernal equinox is also known as "the middle of the day", "day and night", "the month of mid-spring", "the ascending equinox" and so on. The significance of the equinox, one refers to the time of day and night is divided equally, each for 12 hours; the second is the equinox just spring (spring to summer) three months, divided equally in the spring.