Wu Xing (Calendar System)

The theory of the five phases — Wu Xing (五行, "five movements" or "five phases") — is one of the foundational ontological frameworks of Chinese civilization. Unlike the Western four elements, Wu Xing describes not substances but processes — phases of energy transformation constantly transitioning into one another. The theory took shape during the Warring States period (5th-3rd centuries BCE) and became the basis of all Chinese metaphysics, medicine, and natural philosophy.

The five elements — Wood, Fire, Earth, Metal, and Water — are linked by two primary cycles. The generation cycle (相生, xiang sheng): Wood generates Fire (it burns), Fire generates Earth (ash), Earth generates Metal (from its depths), Metal generates Water (condensation), Water nourishes Wood (growth). The overcoming cycle (相克, xiang ke): Wood overcomes Earth, Earth absorbs Water, Water extinguishes Fire, Fire melts Metal, Metal chops Wood.

In calendrical application, the elements are tied to time: each year, month, day, and hour receives an elemental and stem-branch designation. The Ten Heavenly Stems (Tiangan) carry each element in pairs — in yin and yang polarities. The Twelve Earthly Branches (Dizhi) carry hidden stems within them. This creates the foundation for Chinese chronology and astrological systems — primarily BaZi (#10), which uses Wu Xing as its main interpretive matrix.

In Errarium, Wu Xing in its calendrical application is treated separately from its medical application (#25): the same theoretical foundation, but different domains and instruments. The closest analogues by function are Western astrology (#1) and Tibetan elemental astrology (#39); in terms of ontology, it is a unique structure with no direct counterparts in other traditions.