Jing Fang built the most fully worked out of the Han systems that tie the Book of Changes to the movement of time. Four hexagrams were set aside to govern the solstices and the equinoxes, and the remaining sixty were distributed across the days of the year, each holding the position for a fixed span, so that any given day had a hexagram and any hexagram had a season. On top of that he arranged the sixty four into eight palaces, one for each trigram, generated by changing the lines of a governing hexagram in a fixed order, which turned the set from a list into a system with an internal logic.
The third component is the one that survived. Under the method called na jia, the ten heavenly stems and the twelve earthly branches are attached to the individual lines of a hexagram, which gives every line an element, a direction and a place in the sexagenary cycle. That is what allows a diviner to read a changing line as a specific relationship in time rather than as a general image, and it is the technical basis of the coin divination method still practised as Liu Yao. A practitioner today casting three coins six times is using an apparatus assembled in the first century BCE.
None of this was fortune telling in the modern sense. Han specialists understood the arrangement as a description of how the year actually works, so that reading a hexagram meant reading the state of the world at a particular moment rather than consulting an oracle about a private matter. The technical apparatus outlived the cosmology that justified it, which is why a system built to model the seasons is now used almost entirely for personal questions.