Sanyang Kaitai wins in all directions. What poem is it? How come?

This is just a greeting or couplet, not a poem. The meaning of "Three Yang Kai Tai" comes from the Book of Changes, which holds that the solstice in winter is "one Yang Sheng", the December is "two Yang Sheng" and the first month is "three Yang Kaitai". "Three yang" means that the yin gradually disappears, the yang gradually grows, winter goes and spring comes, and everything recovers. "Kaitai" means good luck and prosperity, which means good luck is coming. The rise of human yang has a similar gradual process, and human health is called "three yang qi tai", that is, exercise must yang, be good at yang, and enjoy yang.

The sun is shining, the sun is full, there is good luck in all directions, and everyone will win.