Hai (亥) Earthly Branch: the Pig, Winter Water and Hidden Wood

一 What it is

The Hai (亥) Earthly Branch is one of the twelve zodiac branches in the Chinese calendar system, often nicknamed the Pig. Think of it as a seasonal container that holds a specific blend of energies—like a labeled jar in a pantry that always contains the same ingredients, regardless of which recipe you are cooking today. Hai corresponds to Yin Water, the tenth solar month from Lidong to Daxue (early November to early December), and the true solar hour from 21:00 to 23:00. Its hidden stems are Ren Water with a weight of 1.0 and Jia Wood with a weight of 0.5. For the underlying framework, see Earthly Branches in Bazi: The Twelve Characters and Their Hidden Stems.

In a BaZi chart, Hai appears as the bottom character of a pillar. It participates in several structural relationships: the Yin-Hai combination, the Hai-Mao-Wei Wood triad, and the Si-Hai clash. It is important to note that Hai is not Gui: the branch's polarity differs from the polarity of its main hidden stem. Hai does not guarantee any transformation, nor does its presence imply a specific personality outcome. This article explains what Hai is, where you see it in a chart, how its hidden components are counted, and how to interpret its presence with practical context rather than dramatic conclusions.

二 Where to find it in your chart

To see Hai in your own chart, go to https://bazi-calculator.org/ and enter your birth data. After calculation, inspect the Four Pillars: each column has a top (Heavenly Stem) and bottom (Earthly Branch) character. Hai appears as the bottom character 亥 in any of the four positions—Year, Month, Day, or Hour.

In the results, locate the Four Pillars section. The bottom character of each column is the Earthly Branch. If any of those four bottom characters is 亥, then Hai is present in that position. No additional star section is needed to confirm its presence; the branch itself is the only requirement. An unknown birth hour leaves the Hour pillar unassessable for branch purposes.

三 How to read it

The calculator uses a fixed lookup table for Hai's hidden stems. Hai contains two hidden Heavenly Stems: Ren Water with a weight of 1.0, and Jia Wood with a weight of 0.5. These weights are this calculator's convention for balancing contributions. The main hidden stem is Ren, which is Yang Water. Note that Hai's branch polarity is Yin, but its primary hidden stem is Yang—this is a normal discrepancy, not an error. The method is easier to compare with Xu (戌) Earthly Branch: the Dog, Dry Earth and Hidden Fire.

In BaZi, the Day Master is defined as the top stem of the Day pillar. Ten Gods describe the relationships between that Day Master stem and all other stems—both visible stems in other pillars and hidden stems inside branches. For a Jia Wood Day Master, Ren Water is always the Indirect Resource, and hidden Jia Wood is always a Friend. This is a fixed relationship, not a variable one. For a Jia Day Master, hidden Jia Wood cannot be a Rob Wealth; Rob Wealth applies only to Yin Wood stems like Yi.

When Hai appears in a chart, it contributes Ren Water and Jia Wood to the weighted totals. The weights include all visible non-Day stems plus all hidden stems from every branch. The Day Master stem itself is excluded from ten-god totals, though its element still counts in five-element analysis. Positional context matters because the same Hai in the Year pillar versus the Hour pillar interacts with different neighboring stems and branches. Hai forms a combination with Yin (寅) and a triad with Mao and Wei. It also clashes with Si (巳). These are structural observations used in traditional interpretation, not deterministic predictions. A combination does not automatically transform the chart or change weighted totals; it is a lens for reading relationships, not a mechanical event.

Reading Hai in Sequence

A useful order for interpreting a Hai result is: confirm position, confirm hidden contents, confirm visible stems, then read relationships. First, note which pillar holds 亥 and whether it repeats. Second, list Hai's hidden Ren Water (1.0) and Jia Wood (0.5) as separate contributions. Third, scan the visible top stems for Ren or Jia, because a visible Ren or Jia is a different observation from a hidden one. Fourth, check for Yin, Mao, Wei, and Si in the other branches. This sequence keeps the branch's fixed contents separate from its structural pairings.

四 When it plays out differently

Hai in the Year Pillar

Find 亥 under Year, then check whether it also appears elsewhere. Each occurrence contributes its own hidden Ren and Jia in the raw tally; a repeated branch does not replace the first. A Year Hai does not establish a winter birth, because the Month branch supplies the seasonal position. This distinction is easy to verify by comparing the two columns. Traditional readings connect the Year position with background and early environment, while the element relationships still depend on the Day Master. This point connects directly with Zi (子) Earthly Branch: the Rat, Yang Water, and What It Means in Your Bazi Chart.

Hai in the Month Pillar

When 亥 is under Month, it places the birth between Lidong and Daxue, the tenth solar month. Check the Month column, then scan all four top stems for Ren or Jia. Their presence in the top row is a separate observation from their being hidden inside Hai. In particular, do not expect a yang Ren or Jia stem to pair directly with yin Hai in the same pillar. Traditional winter context informs the reading, but raw totals alone do not establish a strong Day Master.

Hai with Si Clash

Scan the four branches for both 巳 and 亥 and record their columns. Their co-presence identifies the traditional Si-Hai clash pair; if Si is absent, that particular pair is absent. Compare Hai's Ren and Jia with Si's Bing, Geng and Wu rather than describing the result only as Water against Fire. The raw tally retains each branch's contents. Traditional readers may investigate tension or change through this pairing, but its presence does not provide an event, a date, or a reason to assume trouble.

Year Hai versus Month Hai

A Year Hai and a Month Hai share identical hidden contents but differ in seasonal and positional context. Month Hai places the birth between Lidong and Daxue, the tenth solar month, so the chart's seasonal frame is winter. Year Hai does not establish a winter birth on its own; the Month branch supplies that. When both appear, each contributes its own Ren and Jia to the raw tally. Traditional readings associate the Year position with background and the Month position with the immediate seasonal environment, but the ten-god sums remain the same per occurrence.

True Solar Hour and the Hour Pillar

Hai also corresponds to the true solar hour from 21:00 to 23:00. If the Hour branch is 亥, the birth time falls in that window after true solar adjustment. An unknown birth hour leaves the Hour pillar unassessable, so no Hour Hai can be confirmed. When the Hour branch is Hai, its hidden Ren and Jia are counted like any other branch occurrence. The hour position is traditionally linked to later-life and output themes, but the weighted contribution is identical to a Hai elsewhere.

Visible Ren or Jia Outside Hai

Ren or Jia cannot pair directly with yin Hai as the same pillar, because valid stem-branch pairs match polarity, and Ren and Jia are yang while Hai is yin. However, a visible Ren or Jia may appear in other visible stem positions. In Chart A, the visible Year stem is Ren, which adds 1 to Indirect Resource independently of the hidden Ren inside Month Hai. In Chart B, no non-Day visible Ren or Jia appears; the Year, Month, and Hour stems are Geng, Ding, and Yi. This difference changes how the support configuration reads even though both charts contain a Month Hai.

五 Worked chart examples

These teaching examples were screened from the calendar engine. They do not describe clients or claim life events. Tables and weights are generated by code using the calculator’s rules.

Chart A has four pillars: Year 壬戌, Month 辛亥, Day 甲寅, Hour 辛未. The Day Master is Jia Wood, so we exclude the Day Master stem from weighted ten-god totals—though its element remains in the engine's five-element totals.

Step-by-step audit for Hai: the Month branch is 亥. Its hidden stems are Ren Water (1.0) and Jia Wood (0.5). The Year branch 戌 contains Wu Earth, Xin Metal, and Ding Fire. The Day branch 寅 contains Jia Wood, Bing Fire, and Wu Earth. The Hour branch 未 contains Ji Earth, Ding Fire, and Yi Wood.

Now check the weighted ten-god totals provided: Indirect Resource is 2, Indirect Wealth is 1.3, Direct Officer is 2.5, Hurting Officer is 0.8, Friend is 1.5, Eating God is 0.5, Direct Wealth is 1, Rob Wealth is 0.3. These numbers come from summing hidden stems across all four branches, excluding the Day Master stem. The visible year stem Ren adds 1 to Indirect Resource, and the visible month and hour stems Xin each add 1 to Direct Officer, totaling 2. Hai contributes Ren Water (Indirect Resource for a Jia day stem) and Jia Wood (Friend). The remaining totals come from other branches. No transformation or combination is applied here.

Chart A's support configuration combines a visible Year Ren with two visible Xin stems in Month and Hour. The visible Ren adds 1 to Indirect Resource, and each visible Xin adds 1 to Direct Officer, giving 2 from the two Xin. Month Hai contributes its hidden Ren (1.0) to Indirect Resource and hidden Jia (0.5) to Friend. The Day branch 寅 adds hidden Jia to Friend and hidden Bing to Eating God, while Year 戌 and Hour 未 contribute Earth and Fire hidden stems. The resulting Indirect Resource total of 2 reflects the visible Ren plus the hidden Ren in Hai, with no other branch supplying Ren.

This configuration places visible Indirect Resource and visible Direct Officer in the top row while the Friend contributions counted here come entirely from hidden stems. The two Xin stems are both Direct Officer for a Jia Day Master, so the visible stem layer is weighted toward Officer and Resource rather than Friend or Rob Wealth. Hidden Jia appears in both Hai and 寅, giving Friend contributions from two branches. The audit check is to confirm that the visible Ren is counted once and the hidden Ren inside Hai is counted separately, and that neither is merged with the other.

Chart B has four pillars: Year 庚申, Month 丁亥, Day 甲辰, Hour 乙丑. The Day Master is again Jia Wood. The Month branch is 亥, so Hai is present in the Month position.

Audit the hidden stems: Hai contains Ren Water (1.0) and Jia Wood (0.5). The Year branch 申 contains Geng Metal, Ren Water, and Wu Earth. The Day branch 辰 contains Wu Earth, Yi Wood, and Gui Water. The Hour branch 丑 contains Ji Earth, Gui Water, and Xin Metal.

The provided weighted ten-god totals are: Seven Killings 2, Indirect Resource 1.5, Indirect Wealth 1.3, Hurting Officer 1, Friend 0.5, Rob Wealth 1.5, Direct Resource 0.8, Direct Wealth 1, Direct Officer 0.3. For a Jia day stem, Ren Water is Indirect Resource, so Hai adds 1.0 to that category. The hidden Jia Wood in Hai adds 0.5 to Friend. The visible year stem Geng adds 1 to Seven Killings, the visible month stem Ding adds 1 to Hurting Officer, and the visible hour stem Yi adds 1 to Rob Wealth. The Day branch's hidden Yi Wood counts as Rob Wealth, not Friend, because Yi is Yin Wood and Jia is Yang Wood. No star or combination alters these sums.

Chart B's support configuration differs materially: the visible stems are Year Geng, Month Ding, and Hour Yi, with no non-Day visible Ren or Jia. Indirect Resource comes only from hidden Ren in Hai (1.0) and hidden Ren in 申 (0.5), totaling 1.5. Friend comes only from hidden Jia in Hai (0.5). Rob Wealth reaches 1.5 through hidden Yi in 辰 plus visible Hour Yi, and Seven Killings reaches 2 through visible Year Geng plus hidden Geng in 申. The Month Ding adds 1 to Hurting Officer.

Compared with Chart A, Chart B has no visible Resource or Friend contribution outside the Day Master column. Its Resource and Friend support is entirely hidden, while its visible layer carries Seven Killings, Hurting Officer, and Rob Wealth. Chart A, by contrast, shows visible Resource and visible Officer with hidden Friend support. Both charts contain a Month Hai contributing the same hidden Ren and Jia, yet the surrounding visible stems produce two different support pictures. The audit check is to trace each ten-god total back to its visible or hidden source rather than assuming the Month Hai dominates the reading.

六 How common is this configuration?

Across all 518,400 possible Four Pillars combinations in the enumeration used here, 亥 appears in 29.3933% (152,375 combinations). A chart is counted once if it contains at least one match.

This is an equal-weight combination-space proportion, not a percentage of people and not the frequency in a birth registry. We enumerate 60 year pillars, 12 solar-month slots, 60 day pillars and 12 hour slots, with the paired stem rules respected. Calendar duration, birth timing and unknown hours are not population-weighted.