The ten stems

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.