Zhou Yi is the original core of the I Ching or Yi Jing. We don’t know exactly when it was written but archaeological evidence clearly indicates that it was written in the Western Zhou period. (1045-771 B.C.E.)
The earliest text where the Zhou Yi is mentioned is the Zuo Zhuan in a chapter about a divination performed in 675 B.C.E. We know now that the Zuo Zhuan is a much more reliable source than scholars previously thought because an excavated version has been confirmed to be from ca. 400 B.C.E. Therefore it is beyond doubt that the Zhou Yi was written before 675 B.C.E. which place it in the Western Zhou period!
There are different versions of the text described in my book and other places. The basis for the present translation is the so-called received version. The main reason is that all parts of the Zhou Yi mentioned in the Zuo Zhuan is identical to the received version. But it is clearly also the most coherent and logical version.
What happened to the I Ching over time is described by Richard J. Smith in Fathoming the Cosmos and Ordering the World – The Yijing (I Ching or Classic of Changes) and Its Evolution in China (2008).
Any conceivable concept you come across with relation to The I Ching is probably mentioned in Bent Nielsen’s Companion to “Yi Jing” Numerology and Cosmology.
How people have conceived the I Ching over time is a huge subject. But, in fact, there is not so much to say about the origin of the Zhou Yi before it was mentioned in the Zuo Zhuan. Before that we know of hexagrams incised and written on bones, bronzes and pots. We just don’t how exactly how they were related to the Zhou Yi.
The yarrow method described in this site is the most ancient we know of. It is described in further detail in my book.
The fact is that this wonderful and inspiring text survived the book burnings of the Qin dynasty and it has had an enormous impact on philosophical thought in China up to this day.