辛 Xin
Yin Metal, jewellery, the refined blade, worked silver. Metal that has been finished: precise, discerning, and conscious of how things look.
What a Xin day master is
Yin Metal is Geng after the polishing. It values refinement, precision and beauty, and it has a low tolerance for the crude or the careless. Xin people notice the detail nobody else registered and often carry unusually high standards for themselves first.
In Chinese astrology your core element is Yin Metal, pictured as the finished jewel. You are refined and exacting, and you choose quality over quantity in everything. Your standards are the point, not the problem.
Xin at its best, and where it strains
Strength. Discernment and craft. Xin produces work with nothing sloppy left in it.
Difficulty. Polished things fear scratches. Xin can be thin-skinned about criticism and can let standards curdle into a fastidiousness that stops anything shipping.
Xin shares its element with Geng, the yang form of Metal, and the two behave nothing alike. That is the whole reason BaZi uses ten stems rather than five.
The four relationships every BaZi reading runs on
Your day master is not read alone. Everything else in the chart is judged by how it treats Metal, and the five elements move in two cycles: one that nourishes and one that restrains. For a Metal day master those come out as follows.
A chart with plenty of Earth and little Fire reads very differently from the reverse, even with the same day master. That balance is what a BaZi practitioner is actually looking at, and it is why two Xin people can be unrecognisable to each other.
BaZi pillars here use the solar calendar the tradition uses, so the year turns at Lichun in early February rather than at the lunar new year, and the hour pillar follows the late-Zi convention.