The amazing caculator that use for Chinese ancient astrology is here. It's not only in fiction.
There is often a mysterious person in Wuxia fiction who can make prediction, for example, the fate of leading character, the develpment of Wuxia world in the future. This person often have a special caculator to use. It is full of Chinese ancient wisdom and seldom people have knowledge on it. Most people think it just fiction, however, it's real.