 winter solstice were assumed to occur at midnight on a day with a <a href="sexagenary.html">sexagenary</a> day cycle of ji&#462; z&#464;. The epochs were not determined by examining observation data from the past, but calculated based on the observed positions of the Sun and Moon and the cycles of their motions. Near the end of the western Han dynasty in the first century BC, Li&#250; X&#299;n (劉歆) used the <i>I Ching</i> or <i>Book of Changes</i>, an ancient Chinese divination text, to explain the ast