There were four farewells and four unique days. What are the four departure days and four unique days?

The day before the vernal equinox, autumnal equinox, summer solstice and winter solstice is called "leaving the sun". There are four such days in a year, so it is called "leaving the sun".

"Yumen Jing" said: "Those who leave, Yin and Yang are separated from the day before yesterday." These points are vernal equinox and autumnal equinox, even summer solstice and winter solstice. The day before means the day before. Those who leave four times on the day before the vernal equinox are called Li Mu. The day before the summer solstice is called the fire prevention period; The day before the autumnal equinox is called the golden calendar; The day before the winter solstice is called "water dividing day" The four separation days must be written in the "Yellow Calendar", which is the day before beginning of spring, Changxia, beginning of autumn and beginning of winter in the four solar terms, and is called "Four Separation Days". "Yumen Jing" says: "Four departures from Japan are the day before four departures." In fact, it means "Wang Mushui in beginning of spring is absolutely unique, Huo Wangmu in the long summer is absolutely unique, Jin Wang soil in beginning of autumn is absolutely unique, and Shui King Wang in beginning of winter is absolutely unique. Therefore, the first day is also unique. " If the date you choose for your wedding or engagement is a "unique day", there is absolutely nothing to envy, so be sure to check it carefully on the calendar! Metaphysics believes that the fourth day of departure from the sun and the fourth day of departure from the sun are the time when the four seasons intersect and the seasons change from yin to yang. This reminds me of the research on chaos mechanism in the frontier science and technology field in recent years, and thinks that when the system reaches a certain critical value, there will be order and chaos between the systems. Is there any connection between the two? In the culture of choosing dates, there are eight days in a whole year, which you can't even think about.