BaZi Hour Stem Table: Find Your Hour Pillar Step by Step

Short answer: A BaZi hour stem table maps the 12 two-hour branches of the day against five groups of day stems to produce the hour stem for any birth time. Your hour pillar is built from two parts: the hour branch, which comes from the clock time, and the hour stem, which comes from your day stem — not your year stem. Find your day stem, find your birth-hour branch, read across the table, and you have your hour pillar. The full table appears below, along with the formula that generates it, two worked examples, and a worksheet so you can verify the method yourself.

This guide approaches BaZi (Four Pillars of Destiny) as a traditional Chinese cultural and reflective practice. It is not a scientifically validated method of predicting personality or life events. Treat what follows as an explanation of traditional calendar arithmetic, not a prediction.

Key Takeaways

• The hour pillar's branch comes from the clock: the day is divided into 12 two-hour blocks, starting with Zi (子) from 23:00 to 01:00.
• The hour pillar's stem is determined by the day stem — the stem of the day you were born — never by the year stem.
• Five day-stem groups each produce a fixed sequence of 12 hour stems, giving the complete 12 × 5 hour stem table.
• The table can be generated by a single formula: hourStemIndex = (2 × (dayStemIndex mod 5) + hourBranchIndex) mod 10, using zero-based indexes.
• Because the Zi hour straddles midnight, and because traditional practice often uses local solar time, clock-time conversions carry real ambiguity you should flag rather than paper over.

What the Hour Pillar Is and Why It Matters

A BaZi chart, sometimes called a Four Pillars chart, has four columns: year, month, day, and hour. Each pillar combines one of the ten Heavenly Stems (天干) with one of the twelve Earthly Branches (地支). The hour pillar is the fourth column, and in traditional interpretation it is associated with later life, children, and inner or private tendencies. Whether or not you give those associations weight, the hour pillar is required to complete a chart — and it is the pillar beginners most often get wrong.

The reason is that a clock time alone does not tell you the hour stem. You also need the day stem, because the starting point of the hour-stem sequence depends on it. The month stem has a related dependency on the year stem. A calendar or calculator can resolve these relationships; this table makes the hour calculation visible.

If you are brand new to the chart structure, the Chinese birth chart beginner's guide walks through all four pillars before you dive into hour arithmetic.

The Ten Stems and Twelve Branches: Indexing Conventions

Everything below uses zero-based indexing, which matches how the cycle actually counts. Commit these two lists to memory and the rest is mechanical.

The ten Heavenly Stems (index 0–9):

The twelve Earthly Branches (index 0–11), with traditional clock ranges:

Two conventions deserve explicit statements, because they are the source of most beginner errors and honest practitioners disagree about them:

1. The midnight question. The Zi hour runs from 23:00 to 01:00, straddling midnight. Some traditions treat the day as changing at 23:00 (so 23:30 belongs to the next day's day pillar), while others change the day at 00:00 as civil clocks do. Neither is "the" answer; classical texts and modern schools differ. State which convention you are using, and if a birth time falls between 23:00 and midnight, note that the chart is convention-sensitive.
2. Solar time. Some schools apply the ranges to local solar time; others use civil time. Someone born at 11:10 clock time could fall in the Si hour after a sufficient negative solar correction. The correction depends on longitude, the historical clock offset and the equation of time. Record the calculator's convention instead of treating one school's input handling as universal.

The Hong Kong Observatory's reference page on Heavenly Stems and Earthly Branches documents the standard pairing of branches with two-hour periods and their role in traditional Chinese timekeeping, and is a reliable external anchor for the clock ranges above.

The Complete BaZi Hour Stem Table

Here is the full table. Rows are the twelve hour branches; columns are the five day-stem groups: Jia/Ji, Yi/Geng, Bing/Xin, Ding/Ren and Wu/Gui. The two stems in each group are five positions apart in the ten-stem sequence. They do not share the same element or polarity; they share the same remainder when their zero-based indexes are divided by five.

Notice the pattern in the Zi row: the Zi-hour stems run Jia, Bing, Wu, Geng, Ren — every other stem, all yang. Each column then steps forward one stem per hour branch, wrapping after Gui to Jia. Compare all five groups directly with Table 5 of the Hong Kong Observatory's stems-and-branches reference, which documents the relationship between day stems and hour stems. This supports the calendar table, not astrological interpretations.

The Formula Behind the Table

You never need to memorize the table if you can remember one line of arithmetic:

hourStemIndex = (2 × (dayStemIndex mod 5) + hourBranchIndex) mod 10

Where it comes from:

• dayStemIndex mod 5 collapses the ten day stems into the five groups: Jia(0)/Ji(5) → 0, Yi(1)/Geng(6) → 1, Bing(2)/Xin(7) → 2, Ding(3)/Ren(8) → 3, Wu(4)/Gui(9) → 4.
• Multiplying by 2 gives the Zi-hour starting stem for that group: 0 → Jia, 1 → Bing, 2 → Wu, 3 → Geng, 4 → Ren. This is the step of two yang stems per group you can see in the Zi row.
• Adding hourBranchIndex walks forward one stem per two-hour block.
• mod 10 wraps the cycle.

Check it against the table: a Bing day (index 2) gives 2 × (2 mod 5) = 4, so the Zi hour is stem 4, Wu — matching the Wu Zi entry. A Gui day (index 9) gives 9 mod 5 = 4, times 2 = 8, so Zi hour is stem 8, Ren — matching Ren Zi. The formula and the table are the same object in two forms, which is why a good hour stem table can always be regenerated rather than looked up.

Why the Day Stem, Not the Year Stem

This is the single most important rule on this page, and the most common beginner mistake. The hour stem is derived from the day stem — the stem sitting on top of your day pillar — and never from the year stem.

There is a useful parallel: the month stem is keyed to the year stem, while the hour stem is keyed to the day stem. These are separate rules, not a general formula for every calendar unit. Substituting the year stem in the hour formula can select the wrong column, even if the final result sometimes happens to agree.

Practically, this means the workflow has an order: you must determine the day pillar first (from a calendar or calculator), read its stem, and only then consult the hour stem table. A birth date and clock time alone are insufficient until the day pillar is established. If you want a tool that handles the calendar lookups, the hour boundaries, and solar-time correction for you, you can open the BaZi calculator and enter a birth date and time — it will place all four pillars, and you can check its hour pillar against the table above as a learning exercise.

Worked Example 1: Geng Day, Shen Hour

Hypothetical example.

Suppose a hypothetical person's chart has a Geng (庚) day stem, and they were born at 16:20, which falls in the Shen (申) hour, 15:00–17:00.

Step 1 — locate the day-stem group. Geng is index 6. 6 mod 5 = 1, so this is the Yi/Geng column.

Step 2 — locate the branch row. Shen is branch index 8.

Step 3 — apply the formula. hourStemIndex = (2 × 1 + 8) mod 10 = 10 mod 10 = 0 → Jia.

Step 4 — read the table. Yi/Geng column, Shen row: Jia Shen (甲申). The formula and the table agree.

Step 5 — check the conventions. 16:20 is 80 minutes after 15:00 but only 40 minutes before 17:00. A positive correction of 40 minutes reaches the You-hour boundary; a negative correction greater than 80 minutes moves before Shen. Do not call this result stable until you have checked both the direction and size of the actual correction. Here we assume 16:20 is already the time chosen for the calculation.

Worked Example 2: Ji Day, Wu Hour

Hypothetical example.

Now consider a hypothetical Ji (己) day stem with a birth time of 12:05, inside the Wu (午) hour, 11:00–13:00.

Step 1 — day-stem group. Ji is index 5. 5 mod 5 = 0 → the Jia/Ji column.

Step 2 — branch. Wu is branch index 6.

Step 3 — formula. hourStemIndex = (2 × 0 + 6) mod 10 = 6 → Geng.

Step 4 — table. Jia/Ji column, Wu row: Geng Wu (庚午). Agreement again.

Step 5 — conventions. 12:05 is near solar noon, but clock noon and solar noon rarely coincide exactly. In a location where solar time runs 15 minutes behind clock time, the solar reading is 11:50 — still Wu. In an extreme case (far western China on Beijing time, for instance), corrections can exceed an hour, and a noon birth could flip between Si and Wu. This is precisely the situation where you should state the convention you used rather than assert a single pillar with false confidence.

Common Mistakes and How to Avoid Them

Using the year stem. Covered above, but worth repeating: the hour stem key is the day stem, full stop.

Treating Zi as an ordinary hour. Zi is the only branch that straddles two civil dates. A birth at 23:40 on June 10 may be a June 10 chart or a June 11 chart depending on the school. Record both possibilities if the time falls in that window; do not silently pick one.

Ignoring timezone edges. A timezone can cover a wide range of longitudes. Check the actual correction against both neighboring boundaries; a fixed 30- or 45-minute safety margin is not reliable everywhere.

Off-by-one indexing. If your hand calculations consistently disagree with the table by one stem, you are probably counting Jia as 1 instead of 0. The cycle is zero-based in this presentation because the modular arithmetic then works cleanly.

Assuming the table is universal across all schools. The five-column structure itself is standard and appears consistently in classical and modern references, but the inputs — which day, which solar-adjusted hour — are where schools diverge. The table is stable; the interpretation of the birth moment is not.

Practice Worksheet

Use this to build fluency. Answers follow; work each one with the formula first, then confirm against the table.

Part A — identify the column. For each day stem, state its index, its index mod 5, and its Zi-hour stem: (a) Yi, (b) Wu, (c) Xin, (d) Ren.

Part B — full hour pillars. Compute the hour pillar for: (e) a Ding day, Mao hour (05:00–07:00); (f) a Jia day, Hai hour (21:00–23:00); (g) a Gui day, Chou hour (01:00–03:00).

Part C — boundary judgment. (h) A birth at 10:50 clock time, in a city where solar time is 25 minutes behind clock time, on a Ren day. Which hour branch applies after correction, and what is the pillar? (i) A birth at 23:20 on a Wu day, using the convention that the day changes at 23:00 — what complication arises, and what would you record?

Answers. (a) Yi: index 1, group 1, Zi stem Bing. (b) Wu: index 4, group 4, Zi stem Ren. (c) Xin: index 7, 7 mod 5 = 2, Zi stem Wu. (d) Ren: index 8, 8 mod 5 = 3, Zi stem Geng. (e) Ding: 3 mod 5 = 3; (2×3 + 3) mod 10 = 9 → Gui Mao. (f) Jia: group 0; (0 + 11) mod 10 = 1 → Yi Hai. (g) Gui: group 4; (8 + 1) mod 10 = 9 → Gui Chou. (h) Solar time ≈ 10:25 → Si hour; Ren: group 3; (6 + 5) mod 10 = 1 → Yi Si. (i) Under the 23:00 day-change convention, the day pillar may belong to the next day, which would change the day stem and therefore the entire hour-stem column — record the birth time, the convention, and both candidate pillars.

Frequently Asked Questions

Do I use the year stem or the day stem for the hour pillar? Always the day stem. The hour stem table is keyed to the day stem's group of five. Using the year stem is the most common beginner error and will produce a wrong hour stem most of the time.

Why does the Zi hour start at 23:00 instead of midnight? In the traditional double-hour system, Zi is centered on midnight, so it runs from 23:00 to 01:00. Schools then differ on whether the day pillar changes at 23:00 or at 00:00. Both conventions exist in the literature; the careful approach is to note which one you used whenever a birth time falls in the late Zi window.

What if I don't know my birth hour? Then the hour pillar is genuinely unknown. Leave it blank rather than interpreting a placeholder as a real hour. You can examine the date-based pillars provisionally, but births near a day or solar-term boundary may leave those uncertain too. Tools should disclose the missing input and any assumptions.

Does daylight saving time affect the hour branch? It can. Use the historical clock offset for the birth location and date; daylight-saving shifts are not universally one hour. Removing a clock shift alone does not establish apparent solar time. Any longitude and equation-of-time correction must also follow the stated method. Do not pre-correct inputs if the calculator already handles them.

Is the hour stem table the same in every tradition? The five-column table itself is consistent across mainstream references, since it follows directly from the sexagenary cycle. What varies is the input handling: midnight conventions, solar-time corrections, and whether the birth location's longitude is applied. When two charts of the same person disagree on the hour pillar, the disagreement is almost always in those inputs, not in the table.

Putting It Into Practice

The hour stem table looks like a memorization task, but it is really three small ideas: branches come from the clock, stems come from the day, and one modular formula ties them together. Learn the Zi-row pattern (Jia, Bing, Wu, Geng, Ren across the five day-stem groups), and you can reconstruct the entire table on a napkin. More importantly, learn the judgment calls — midnight conventions, solar-time corrections, unknown hours — because those are where accuracy is actually won or lost.

If you would like to see your own pillars computed with location and timezone solar correction applied, you are welcome to open the BaZi calculator and compare its hour pillar against your hand calculation from this page. And if you enjoy daily reflective practices built on traditional systems, the daily reading page offers a lighter entry point. Either way, treat the chart as a mirror for reflection — a centuries-old framework for thinking about timing and temperament — rather than a prediction machine, and it will serve you well.

Related guides

For a different part of the process, see Day Master identification and unknown and borderline birth times.

How this guide was created

Published by BaziPal. This guide was drafted with Kimi and checked and edited with an AI coding assistant for calculation consistency, source attribution, product links and cautious wording. It has not been independently reviewed by a credentialed BaZi or tarot practitioner. AI-assisted checks can miss errors.

Calendar references support the stem-branch cycle and solar-term definitions; they do not validate divination or personality claims. Links to practitioner sites document their conventions, not scientific evidence. Hypothetical examples are teaching illustrations, not client results.

These guides explain cultural traditions and offer optional reflection exercises. They are not medical, legal, financial or relationship assessments. For a correction, use the contact details in our privacy policy and include this article's URL and the passage in question.