The definition of the solar time and time, just like other units, is based on a measurement standard, like: meters, kilograms, and points.
As the earth rotates around the sun, its position changes, determines the length of the "day", and also forms "season" and "year." These words still retain the ancient idea of ​​the Earth as the center of the universe, the so-called geocentric theory; also because of this, people still say sunrise, sunset, but in fact the position of the sun in the solar system is fixed.
Every year, the earth orbits the sun around its orbit for a total of 365 days, 5 hours, 48 ​​minutes and 45 seconds (an average of 365.2425) days. This is the so-called "return year." A calendar year has a total of 365 days; every four years - when days are divisible by 4 - February will be increased by one day to make up for the 5 hours, 48 ​​minutes and 45 seconds deleted in the calendar year.
The length of the day varies from 8 hours to 16 hours, depending on the season; the more obvious the four seasons in a place change, the greater the distance between a place and the equator. Earth circles around the sun for a year, then rotates around its own axis in 23.9345 hours, and draws an oval shape between the two poles. The slight change in the distance between the Earth's axis and the Sun defines different seasons.
According to ancient Chinese legends, before the birth of Han Wudi, his mother once dreamed that the sun (yang) had penetrated into her own belly. The sun is a sphere made up of hot gas, symbolizing breeding and multiplying and enlisting royal power. However, among the nearly 100 billion stars in our Milky Way galaxy, the sun is only a small one. “Heart 2 (also known as Scorpio a star)†is five hundred times bigger than hers!
Two or five hundred years before the Christian era, Chinese astronomers have identified solar terms such as the equinox and the winter solstice and the winter solstice. These solar terms are extremely helpful in the calculation of the four seasons. The vernal equinox and the autumnal equinox are the days when the sun crosses the plane of the Earth’s equator; the equinox is on March 21 or 22, and the equinox is on September 22 or 23. The length of time between this day and night is exactly the same. As for the summer solstice, it is probably on June 21 and December 21, when the distance between the sun and the equator is greatest.