The four pillars are your birthday, which consists of the year, month, day and time of birth. Four days and four branches, a total of eight words. For example, this year is Geng Yin, Geng (heavenly stem) Yin (earthly branch). The first month of the lunar calendar is silver moon, followed by February, March, April, May, June, July, August, September, October, November and December in Uzuki. The twelve branches correspond to the same. Tiangan can check the perpetual calendar, including the branches of the sun, but Tiangan will be pushed out by mouth. There are formulas for pushing the moon, the sun and the time, which are easy to remember, but I forgot them for too long. If you are interested, I will help you find them.
It is much easier to remember the five elements. Now write down: heavenly stems A, B, C, D (fire) Wuji (earth) Si (gold) Si (water) Di Zhi Zi (water) Ugly (earth) Si (wood) Chen (earth) Shen You (gold). Among them, the branches of Yin and Yang are Yang, and the five behaviors represented are Yang. In the other five days, I can't remember the four soil (Shui Yang) sea (Yin Shui) Yin (Yang Mu) Mao (Yin Mu) Division (Yin Huo) Wu (Yang Huo) Shen (Jin Yang) You (Yin Jin), so I had to look through the books again.
Roughly, if there is a source, please forgive me.