Quick answer: 甲子 is yang wood (甲) sitting on water (子, the Rat). The branch produces the stem, so it sits on its resource star (正印 Direct Resource), at the Bath life stage; its Na Yin is 海中金 (Gold in the Sea).
甲子 (Jia Zi) is pillar number 1 in the cycle of sixty stem–branch pairs. When it appears as the day pillar, the Day Master is 甲 yang wood, sitting on the Rat branch 子. This page explains how the two halves of the pillar relate, what is hidden inside the branch, and how traditional Bazi texts interpret the combination.
| Pillar | 甲子 Jia Zi |
|---|---|
| Stem | 甲 Jia — yang Wood (木) |
| Branch | 子 Zi — Rat, Water; hours 23:00–01:00 |
| Hidden stems | 癸 |
| Life stage of 甲 in 子 | Bath (沐浴) |
| Na Yin (納音) | 海中金 — Gold in the Sea (Metal), shared with 乙丑 |
| Void branches (空亡) | 戌亥 |
| Branch clashes with · combines with | 午 (Horse) · 丑 (Ox) |
The stem: 甲 Jia
The classical description of 甲 comes from the Di Tian Sui (滴天髓):
甲木參天，脱胎要火，春不容金，秋不容土，火熾乘龍，水蕩騎虎，地潤天和，植立千古。“Jia wood reaches to the sky; to shed its womb it needs fire. In spring it does not tolerate metal; in autumn it does not tolerate earth. When fire blazes, it rides the Dragon; when water floods, it mounts the Tiger. With moist ground and harmonious heaven, it stands planted for a thousand ages.”— Di Tian Sui (Drops from Heaven’s Marrow) 《滴天髓》, 天干論. Original text: Wikisource · also on ctext.org (different edition). Translation: bazimethod.
Jia (甲) is yang wood, the tall tree with a trunk. The Di Tian Sui describes it as reaching to the sky and needing fire to “shed its womb” — energy that wants to grow upward and express itself. On the day pillar, this stem is the Day Master — the “self” of the chart that every other character is measured against. The full verse and a ten-gods table are on the Jia Wood Day Master page.
The branch: 子 Zi
Zi (子), the Rat, is the branch of the deepest winter and of midnight. It is pure water and holds a single hidden stem, 癸. The day branch is traditionally called the spouse palace (夫妻宮), the seat closest to the self, so readers look at it for themes of partnership and private life. As a month it corresponds to the 子 month (around the winter solstice, early December to early January).
How the stem and branch work together
The branch’s element produces the stem’s element, so 甲 sits on its own resource (印) star. The seat is supportive: the branch feeds the stem the way a parent feeds a child. Traditional readings associate it with learning, protection and an inward, reflective temperament, and say the spouse palace here brings support.
In the life-stage cycle this is the Bath stage, the infant being washed. Tradition reads it as an unsettled, exposed position and links it loosely with the “peach blossom” idea of charm and attraction; it gives little solid strength.
Hidden stems in 子
Each branch contains one to three hidden stems. Measured against 甲, they take these ten-god roles:
| Hidden stem | Layer | Element | Ten god for 甲 |
|---|---|---|---|
| 癸 | Main qi (本氣) | Water | 正印 — Direct Resource |
The main qi, 癸, is a Direct Resource (正印) — the producing element, opposite polarity; nurture, study and protection. Because 子 holds only one stem, its meaning in this pillar is unusually concentrated.
Element balance
Counting the stem plus the hidden stems (weighting the main qi fully and the minor qi less, one common convention), the pillar leans wood > water, and fire, earth, metal are absent from the pillar itself. That does not mean the chart lacks them — the year, month and hour pillars usually change the picture entirely, and the month branch matters most of all.
Because the strength of 甲 depends above all on the month of birth, the same 甲子 day reads very differently in different seasons: a wood Day Master is strongest in spring and weakest in autumn. The five elements and useful god guides explain how practitioners decide whether a chart wants more of an element or less.
Na Yin: 海中金
In the older Na Yin system the sixty pillars are grouped in pairs, each with a poetic “sound element”. 甲子 and 乙丑 share 海中金, “Gold in the Sea”, a metal image. Note that the Na Yin element (Metal) is separate from the elements of the stem (Wood) and branch (Water); most modern Zi Ping readers use Na Yin as colour rather than as the basis of the reading.
Traditional personality themes
Popular Bazi writing associates 甲 Day Masters with growth, principle and a straightforward manner, and sometimes with upward ambition and a dislike of being bent. On a 子 seat, the 正印 (Direct Resource) star in the spouse palace colours that picture, as described above. These are traditional images, offered for cultural interest. They are not evidence about any real person, and a single pillar never decides a reading — the classics always judge the whole chart, its season and its balance.
Clashes, combinations and void branches
子 clashes with 午 and forms a six-combination (六合) with 丑, said to produce earth. It also belongs to the 申子辰 three-harmony group of water. When those branches appear in the year, month or hour, or arrive in a luck pillar, tradition says the spouse palace is “moved”. See combinations and clashes.
The pillar belongs to the 甲子 decade (旬) of the sixty-cycle, whose two “void” branches (旬空, 空亡) are 戌 and 亥. Many practitioners note when those branches appear elsewhere in the chart or in luck pillars, reading them as weakened or “empty”.
Find your own day pillar
The day pillar cannot be worked out from the Western date alone — it follows an unbroken sixty-day cycle, and a birth after 23:00 may count as the next day in some schools. Enter your birth data in the free Bazi calculator to see yours, then read the chart-reading guide.
Previous in the cycle: 癸亥 Gui Hai · Next: 乙丑 Yi Chou · All 60 day pillars
Keep learning
More in Day pillars, plus core guides — or go back to the Bazi calculator home page.
Classical quotations are copied from the public-domain texts on Wikisource; links let you check every line. English translations are our own. Traditional Bazi statements are reported as tradition, not as fact.