When were the Book of Changes and Huangdi Neijing written? Which is earlier?

The Book of Changes is the oldest and most profound classic in China. It is said that Fuxi's remarks were summarized and revised (at the same time, the Eight Diagrams of the Book of Changes were produced). It is the crystallization of Chinese wisdom and culture for 5,000 years, and is known as "the head of the group classics and the source of the avenue".

Huangdi Neijing, written before the Spring and Autumn Period, is the earliest extant monograph of TCM theory in China. It has a unique position in the classics of Chinese studies and is the only work named after the holy king. It summarizes the medical experience and academic theories before and after the Spring and Autumn Period, absorbs astronomy, calendar, biology, geography, anthropology and psychology before the Spring and Autumn Period, and comprehensively expounds the diagnosis, treatment and prevention of human anatomy, physiology, pathology and diseases by using the theory of yin and yang and the five elements of harmony between man and nature, thus establishing the uniqueness of traditional Chinese medicine.

It has become the theoretical basis and source of medical development in China.

The Book of Changes was written earlier than Huangdi Neijing.