My relationship with the I Ching was complex from the very beginning. Despite repeated re‑reading of the text, in translation and later in the original Chinese, I have never come across anything that looks much like wisdom. Meanwhile, on the internet, whole armies of crazies advanced their theories about the book: that it coded the deep structures of human DNA; that it provided mathematical proof of the Mayan prophecy of the ending of the world; that it might hold the secret to that holy grail of the physicists, a Theory of Everything.
Will Buckingham, in The uncertainty machine (Aeon Magazine)
Traditionally, the I Ching and its hexagrams were thought to pre-date recorded history, and based on traditional Chinese accounts, its origins trace back to the 3rd and 2nd millennia BCE. Modern scholarship suggests that the earliest layers of the text may date from the end of the 2nd millennium BCE, but place doubts on the mythological aspects in the traditional accounts. Some consider the I Ching the oldest extant book of divination, dating from 1,000 BCE and before. The oldest manuscript that has been found, albeit incomplete, dates back to the Warring States period (475–221 BCE). (from Wikipedia: I Ching)