Why is birthdates' calculation completely different from the actual person's personality?

There are also some mistakes. Although there is an old saying that a leopard cannot change his spots, only a birthday is human nature. What happens during the Universiade the day after tomorrow, time will also change a person's personality, so too much emphasis on the eight-character personality may not be comprehensive, and sometimes it will be completely different. People's personality will change with time and people they meet. Some people give people the impression that this person is very awesome and never gives up; But when he meets a person who is better than him, and people praise him seven inches, he immediately becomes a different person. He will pretend to have everything, so people's personality is very complicated, and sometimes eight characters can't be summarized. Some people are usually soft-hearted, but when he goes to a restaurant for dinner, he finds a "Xiao Qiang" in the dish. He has a tough personality and dares to fight!