Heavenly Stems and Earthly Branches, Explained
Heavenly Stems (천간, cheongan) and Earthly Branches (지지, jiji) are the two building blocks of every pillar in a Saju chart. There are ten stems (갑, 을, 병, 정, 무, 기, 경, 신, 임, 계) and twelve branches (자, 축, 인, 묘, 진, 사, 오, 미, 신, 유, 술, 해), and together they form the traditional East Asian sexagenary (60-term) calendar cycle used to label years, months, days, and even two-hour blocks of the day.
Each stem and branch belongs to one of the Five Elements, and each has a Yin or Yang polarity. The twelve branches are also the twelve zodiac animals familiar from the wider Chinese/Korean zodiac — Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, and Pig.
A Four Pillars chart pairs one stem with one branch for each of the year, month, day, and hour of birth, for eight characters total. Beyond their individual element and polarity, stems and branches interact with each other through specific traditional relationships — pairs that combine, pairs that clash, and groups that harmonize — which is where a lot of the nuance in a full Saju reading comes from.
For entertainment and self-reflection purposes only. Not a substitute for professional advice.