Da Liu Ren is a form of Chinese calendrical astrology

Astrology

Astrology consists of a number of belief systems which hold that there is a relationship between astronomical phenomena and events in the human world...

 dating from (at least) the later Warring States period.

Along with the divination methods Qi Men Dun Jia

Qi Men Dun Jia

Qi Men Dun Jia is an ancient form of divination from China, which is still in use in China, Taiwan, Singapore and the Chinese diaspora in Southeast Asia...

 奇门遁甲 and Taiyi

Tai Yi Shen Shu

Tai Yi Shen Shu is one of the three 三式 predictive arts from China, the others being Da Liu Ren and Qi Men Dun Jia.These arts are basically involved in divination and to a certain extent astrology...

 太乙—collectively known as the "Three Styles" (San shi 三式)—Da Liu Ren is considered in China to be one of the highest forms of Chinese metaphysics.

It is called Da Liu Ren because in the Sexegenary cycle there are Six Rens each with a different branch:

壬申 壬午 壬辰 壬寅 壬子 壬戌

Ren Shen, Ren Wu, Ren Chen, Ren Yin, Ren Zi and Ren Xu

In the words of a contemporary Chinese master of Da Liu Ren, the six Ren indicate an entire movement of the sexegenary cycle, during which an event – object may appear, rise to maturity and then decline and disappear.