What does birthday mean? Never understood

In China, the date of birth is a traditional record of a person's date and time of birth. It expresses the year, month, day and time of a person's birth through heavenly stems and earthly branches's two Chinese characters, one column and four columns. This record has eight characters, so it is called "date of birth". Birthday, or eight characters, is actually another way of saying the four pillars of Zhouyi. Four pillars refer to the time when a person was born, that is, year, month, day and hour. When people use "heavenly stems" and "earthly branches" to express years, months, days and hours, such as Jiazi Year, Shen Bingyue, Xin Chou Day, Ren Yin Shi and so on. Contains the basic state of celestial motion when a person is born. There are two words in each column and eight characters in four columns, so fortune telling is also called "measuring eight characters" According to the relationship between Yin-Yang, Five Elements and heavenly stems and earthly branches, it is inferred that the human body is responsible and blessed. However, what I want to talk about here is not how to "measure eight characters", but how to calculate eight characters. In order to get the correct time of birth, the sundial is the most accurate measurement during the day. When the clock time is the artificial average time and regional standard, we must calculate the "apparent solar time difference" according to the ecliptic and the "local longitude time difference" according to the birthplace, so as to get the real astronomical birth time. In the eight characters, the annual and daily branches are continuous and true; The branch of month and time is calculated according to the branch of year and day, which can be said to be virtual. At present, it is common for a numerologist to convert the date of birth (calculated according to the lunar calendar) into the date of birth, which is called carving eight characters. Then it will be understood by numerology. Birthdays are usually used for divination and marriage, and they are still popular among the people. Birthdays are used in marriage to predict whether two people will be happy in their future marriage. Generally speaking, both men's and women's birthdays are born together, which means that they are happy after marriage, and conflict with each other means that they are unhappy. Some people think birthday fruit is very important. If their birth dates coincide, they may give up their marriage with one party. Birthdates can only reflect the day when a person was born at most, and it is not too much to record the time. Some people use birthdays to tell fortune, which is very unreliable. Because a person's fate is influenced by many things, besides the weather, there are also restrictions on the region and people he grew up in. Coupled with the different opportunities, what proportion can the weather affect?