What is the relationship between the eight characters and the official calendar and the lunar calendar?

As early as 2697 BC, when the Yellow Emperor, the ancestor of China, founded the country, heavenly stems and earthly branches was ordered to explore the qi of heaven and earth and the five elements (water, fire and earth in Jin Mu), and opened A, B, C, D, E, Ji, G, Xin, Ren, Gui, Zi, Ugly, Yin, Mao, Chen, Si, Wu and Wei. In the era of the Yellow Emperor, because of the disturbance of the God Chiyou, the Yellow Emperor was worried about the people and fought Chiyou in the land of Zhuolu. Even a hundred miles of bloodshed could not be cured. So the Yellow Emperor fasted and bathed, and built altars to worship heaven and earth. The sky falls ten times (i.e. A, B, D, E, G, N, N). Twelve branches (that is, a letter that ugly Mao Yinchen applied for at noon). The emperor made ten pieces of dry circular cloth look like the sky and twelve pieces of square cloth look like the terrain. At first, doing it for the sky, supporting it for the ground, and then it can be cured. Later, the troublemakers divided the 10-day dry and 12-day branches into 60 Jiazi, and set the founding date of Huang Lai as Jiazi Year, Jiazi Month, Jiazi Day and Jiazi Time. This is the origin of heavenly stems and earthly branches.