What is the origin of the vernal equinox?

1, the vernal equinox, is the fourth solar term in the "24 solar terms". "The vernal equinox, Yin and Yang. So it's hot and cold day and night. " The word "vernal equinox" marks the boundary between day and night, cold and hot. The almanac says, "The bucket refers to the vernal equinox, which is about Sunday. The northern and southern hemispheres are equally divided day and night, which is also half of spring, hence the name vernal equinox." The significance of the vernal equinox, first, refers to the equal division of day and night, each of which is 12 hours; Secondly, traditionally, it is spring in beginning of spring from long summer, and the vernal equinox happens to be in the three months of spring, and spring is equally divided.

2. Twenty-four solar terms are the product of ancient farming civilization in China, and they are the special festivals in the trunk calendar to express natural rhythm changes and establish December architecture. In ancient China, four seasons were divided according to the ebb and flow of Yin and Yang, with 24 solar terms "Li Si" as the beginning of the four seasons and four solar terms "dichotomy to dichotomy" in the middle of the four seasons. For example, in spring, beginning of spring is the starting point, the vernal equinox is the midpoint, and the long summer is the end point. In ancient times, there were only four solar terms in foreign countries: vernal equinox, autumnal equinox, winter solstice and summer solstice. According to the regression movement of the direct point of the sun, four seasons are divided, and the "vernal equinox" is the beginning of the four seasons. For example, spring begins with spring and ends with the summer solstice. Western countries are located at higher latitudes, far from the intersection of Huangchi. Taking "one divided into two" as the starting point of the four seasons can better reflect the local climate in the west than "four stands". The four seasons divided by "dichotomy and dichotomy" abroad are one and a half months later than those divided by China's traditional "Li Si".

3. The vernal equinox, autumnal equinox, summer solstice and winter solstice ("bisection") are the four solar terms reflecting the regression movement of the direct point of the sun. The direct point of the sun makes a regression movement between the Tropic of Cancer and the Tropic of Cancer every year. It is the winter solstice when the sun directly hits the Tropic of Cancer, the vernal equinox when the sun directly hits the equator and moves towards the Tropic of Cancer, the summer solstice when the sun directly hits the Tropic of Cancer, and the autumnal equinox when the sun directly hits the equator and moves towards the Tropic of Cancer. The vernal equinox usually refers to the moment when the sun's apparent yellow meridian is at 0, that is, from March 19 to 22 of the Gregorian calendar every year. In the time period, it also refers to the position of the sun between 0 and 15, that is, from the vernal equinox to Tomb-Sweeping Day, and the Gregorian calendar is between March 20th and April 5th.