Jia Zi · 甲子
Jia Zi pairs 甲, a Yang Wood Day Master, with 子 (the Rat), a Water branch. Read the upper character first, then the branch and the stems it contains.
The Day Master on top
Yang Wood · 甲 — Jia (甲) is the yang form of Wood. Its familiar image is a tall tree: a visible trunk, branches, and upward growth. The image helps explain the symbol's association with direction and structure.
Learn this Day Master's image and relationships →The branch and its hidden stems
子 (the Rat) contains 癸 in the traditional hidden-stem table. Each stem receives a ten-god label by comparing its element and polarity with 甲. The day branch is also traditionally called the spouse palace; that name does not identify a partner's character.
癸
Direct Resource
Yin Water · 癸 → 甲
Na Yin
Jia Zi has the Na Yin label 海中金, "Gold in the Sea". Thirty names are shared by the sixty pairs. This is a separate classification from the Day Master's element.
Stage of the cycle
Bathing · This is the traditional twelve-stage label for the day stem 甲 in branch 子. Read it as a stem–branch classification, not a person's age or state of health.
The two unpaired branches (Xun Kong)
甲子 belongs to the ten-pair group beginning with 甲子. Its ten stems pair with ten of the twelve branches, leaving 戌亥 outside that group. Those two are called Xun Kong, or "void branches".
Keep the Day Master, change the branch
These day pillars share the same upper character. Compare their hidden stems to see why a Day Master alone cannot describe all the chart relationships.
Is Jia Zi actually your day pillar?
Calculate all four pillars from your birth details, then check the day column. Near the day boundary, birth time and the calculator's time conventions can affect the result.
This reference describes one of four pillars. The calculator shows the full chart and the birth details used to produce it.