These eight words stand for year, month and day respectively, such as: Xin Mao is the year, Ding You is the month, Geng Wu is the day, and Bing Zi is the time.
The eight-character "image" and the image of Zhouyi are different in composition. The Book of Changes uses Yin and Yang and the hexagrams composed of these two hexagrams as "images", and the eight characters are symbols composed of Chinese characters. From this perspective, the eight-character image is more similar to the "image" of traditional Chinese medicine.
Although it is composed of Chinese characters, this Chinese character is actually just a symbol here, not a general language or sentence. It's just an elephant. The eight characters are essentially the same as the hexagrams in Zhouyi, except that they use Chinese characters instead of Yin and Yang symbols to form hexagrams.
The basic ideological basis of the eight-character easy-to-image (eight-character fortune-telling) is that heavenly stems and earthly branches represents the Qi of Yin-Yang and Five Elements between heaven and earth, and is a symbol of the Qi of Yin-Yang and Five Elements. They form a "qi" system. The qi of yin and yang and five elements has the functions of generation, combination, restraint, transformation and flushing.
Date of birth, or constellation for short, refers to the calendar date when a person is born. This is actually the same meaning as the birthday we are talking about now.
In fact, the calendar uses heavenly stems and earthly branches to represent the year, month, day and time.
Ten days of work: A, B, C, D, E, Ji, G, Xin, people, ghosts.
Twelve earthly branches: Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai.
This calendar represents time, and heavenly stems and earthly branches has one word for each. In order, it is from Jiazi, Emei ... to Guihai, which is exactly 60 groups in a cycle.
The year, month, day and hour are called "four pillars", and each pillar is represented by "heavenly stems and earthly branches", so it is called "eight characters".