What is the oldest work at present? In what era? (China only)

There are some articles in Shangshu that record the period of Three Emperors and Five Emperors.

Shan Hai Jing was also a neat book in ancient times, and the recorded time was probably before Xia Dynasty.

The Book of Changes is an ancient divination book. According to Records of the Historian, Fuxi did gossip for innate gossip, and later Zhou Wenwang did gossip for the gossip the day after tomorrow. Confucius liked Zhouyi in his later years and made a biography (annotation) for it.