Therefore, the eight trigrams are frequently coordinated with the day, and they can of course also be correlated with the course of the year. ... A cycle of twelve hexagrams from the Book of Changes, the so-called P'i Kua is often also correlated witht he course of the year. ... These eight trigrams, then are coordinated with the times of the day and the cardinal points, and have, in addition, very interesting psychological correlations.