The "eight characters" are also called four pillars (year pillar, moon pillar, sun pillar and time pillar), each of which has two characters, above which are heavenly stems (A, B, C, D, E, Ji, Ke, Xin, Man and Ghost) and below which are earthly branches (Zi, Ugly, Yin, Mao, Chen, Si and Wu).
According to legend, during the period of the Yellow Emperor, China's calendar (now the lunar calendar) was made by the emperor's family and Fu. Since the era of the Yellow Emperor, there have been 78 flowers and 68 flowers. A 60-year-old flower is composed of heavenly stems and earthly branches arranged in turn and combined circularly.