Yang

The ten heavenly stems are one of the two series of the Chinese sexagenary cycle, pairing with the twelve earthly branches to give sixty combinations used to number years, months, days and hours. Each stem is assigned a phase of the wu xing and a yin or yang polarity, so the ten run as the yang and yin forms of the five phases in turn.

The stems are ancient, attested on the oracle bones of the Shang dynasty, where they were already used to name the days of a ten-day week, and they remain a basic element of the Chinese calendar and of the Four Pillars method of fate calculation.

Combined with the twelve branches in a fixed rotation, the ten stems produce the sixty-year cycle that names Chinese years, and in Ba Zi (the Four Pillars of Destiny) the stem and branch of the year, month, day and hour of birth are read for character and fortune. The stem-and-phase pairing ties the calendar directly to the five-phase cosmology.

The atlas gives each stem its phase, polarity and use. The earthly branches it pairs with, and the wu xing phases it expresses, are treated in their own categories under Eastern Systems.