Yin (寅) — Tiger Branch / Yang Wood

Yin is yang wood, hidden stems 甲 (yang wood), 丙 (yang fire), 戊 (yang earth) — a powerful triple of growing, igniting, and rooted force. It is the dawn tiger emerging from the forest, the sap rising in the first month after 立春. Yin people in chart prominence often have entrepreneurial fire, principled assertiveness, and a reluctance to be domesticated.

Yin san-he with 午 and 戌 transforms to fire (寅午戌合化火), and six-unites with 亥 to wood (寅亥合木). It is conflicted by 申 (寅申冲) and forms the 寅巳申 三刑 (the "punishment of impulsiveness").

Half the reason Yin (寅 yín) matters is calendar politics. Classical scholarship describes three competing new years: the Xia calendar began the year with the Yin month, the Shang calendar with Chou, the Zhou calendar with Zi, and a change of dynasty often moved the first month. The later standard calendar kept the Xia arrangement, so the first month is built on Yin and Yin became the real start of the year. Setting the year pillar at Start of Spring is therefore inherited from that calendrical tradition, not invented by fortune-tellers. It follows that the Yin month begins at Start of Spring and not on lunar New Year's Day. The two can sit ten or twenty days apart, and in some years the festival falls before the solar term while in others it falls after. Someone born on the third day of the first lunar month in a year whose Start of Spring lands on the sixth still belongs to the previous year pillar. This is the single most common beginner error, and it does not stop at the year: the direction and starting age of the luck pillars go wrong with it. One qualification belongs here. The overwhelming majority of lineages change the year pillar at Start of Spring, but a minority practice changes it on lunar New Year's Day, and for births between the two dates the charts are entirely different.

The tiger image tempts people to read every Yin as combative, which the classical texts do not support. Yin is early-spring wood, rising in momentum but short on accumulated strength, with the cold not yet gone, so its real character is eagerness on shallow roots. A second simplification treats the Yin and Hai union as automatically becoming wood. Classical method separates a union that transforms from a union that merely binds, and the difference turns on the season and on whether a stem is present to draw the transformation out; most of the time the pair simply hold each other. Yin, Si and Shen resist flat statements in the same way. They carry punishment, union and harm between them in overlapping layers, and while some transmissions foreground the punishment, others hold that the Si and Shen union acts first. Stating that both readings exist is more honest than forcing one.

The Jia, Bing and Wu already named inside Yin are in very different states. Jia wood is at its office stage in Yin, the dominant seasonal qi. Bing fire is at its birth stage, kindled but not yet strong, and Wu earth is conventionally given the same birth position. The combination says that Yin is not plain wood but wood that carries its own spark, and because wood feeds fire while fire warms wood, Yin is unusually useful in a cold chart. When a chart needs fire and no fire stem is visible, a Yin branch is often the hidden supply line.

Yin belongs with Shen, Si and Hai to the four growth positions, the openings of the four seasons, which the symbolic-star tradition calls the travelling horse; for the Shen-Zi-Chen group the horse sits in Yin. The shared character of these four is motion, beginnings and leaving where you are. In practice a Yin in the year or month pillars tends to be read toward early-life relocation and enterprise, and one in the day or hour toward travel, postings and changes of setting experienced personally. The symbolic star is a prompt, though; the conclusion still depends on whether this Yin helps or hinders the day master.