How to calculate the surname of people who get married when they grow up?

Are you sure you're asking about the Book of Changes, not the Five Elements? Well, the divinatory images about marriage in the Book of Changes are Wan (a man marries a woman), Gui Mei (a woman marries a man) and Xian (a man and a woman do that after falling in love). The Book of Changes is a qualitative knowledge, not a quantitative thing, nor is it used for divination-sixty-four hexagrams represent sixty-four things and sixty-four states in the world. When you meet something, do what you say, and you will know good or bad. Don't look at fate, don't count as divination, this belongs to the five elements ... Anyway, my personal opinion is not as useful as the Book of Changes, but I can do it.

Like what? The Book of Changes is like urban planning and architecture, while birthdates' Five Elements is more like a market guide for building materials. I can do both. Which one do you want?