Derive the hour stem with the five-rat rule: a twelve-branch worksheet
Take the day stem, use the five-rat rule to fix the stem paired with the Zi hour, then run the ten stems in order across the twelve branches. For a Xin day: Bing-Xin days start at Wu Zi, so Zi is Wu, Chou is Ji, Yin is Geng, Mao is Xin, Chen is Ren, Si is Gui, Wu is Jia, Wei is Yi, Shen is Bing, You is Ding, Xu is Wu and Hai is Ji. Check the result against the returned example chart: 2005-12-23 08:37 in Asia/Shanghai falls in the Chen interval, the day stem is Xin, the derivation gives Ren Chen, and the returned hour pillar is also Ren Chen. This confirms only that your lookup matches the calculation under those settings; it establishes no interpretation. One caveat: for 23:00–23:59, Wenbu's default 00:00 day boundary keeps the current day pillar but takes the hour stem from the library's next-day convention, so label that case separately.
- The five-rat rule needs only the day stem to fix the Zi-hour stem; the other eleven hours follow in sequence.
- A twelve-cell worksheet makes each step visible so it can be checked cell by cell, not just read off eight characters.
- Confirm date, time zone and day-boundary settings before comparing hour pillars, or a mismatch may come from settings rather than the rule.
- For 23:00–23:59, the default day boundary keeps the current day pillar but takes the hour stem from the next-day convention, so label it separately.
From day stem to twelve hour stems
- 01Fix the inputs
Record the Gregorian date, local clock time, time zone, day-boundary setting and whether true solar time is enabled.
- 02Read the day stem
Take the stem from the day pillar, for example Xin from a Xin Si day, computed under the same settings.
- 03Set the Zi-hour stem
Apply the five-rat rule to find the stem paired with Zi; Bing-Xin days give Wu Zi.
- 04Run the twelve cells
Fill Chou through Hai in stem order; adjacent cells must hold adjacent stems.
- 05Flag late Zi
If the time is 23:00–23:59, mark that cell and read the returned hour stem or compare day-boundary settings.
- 06Compare with the returned result
Match your derived hour pillar against the tool's; if they differ, check settings first.
What the five-rat rule actually does
The five-rat rule is a traditional lookup: the day stem determines which heavenly stem is paired with the Zi hour, and from there the ten stems are assigned in order to Chou, Yin, Mao and on through Hai. The mnemonic groups the ten day stems into five pairs, each with one starting stem, so you memorise five lines rather than sixty combinations one by one. It is a fixed step in chart construction, a traditional convention rather than a claim about a person's fate.
Before using it, confirm the day stem, which depends on the day pillar. The day pillar in turn depends on the recorded time, time zone and day-boundary setting. Wenbu's published notes state that the day and hour pillars use the selected local clock time by default, with a 00:00 day change. Fix those inputs first, or the day stem itself may differ and the rule cannot be checked.
Filling the twelve-cell worksheet
Lay the twelve branches across the top in order: Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai. Put the day stem at the left. The first cell holds the Zi-hour stem given directly by the rule; each later cell takes the next stem in the ten-stem cycle, wrapping from Gui back to Jia. Twelve cells therefore run slightly past one full cycle, which is expected and needs no correction.
Run two self-checks afterwards. Adjacent cells must hold adjacent stems, so a jump means a copying error. The Zi and Wu cells sit six positions apart, which gives a second cross-check. The worksheet's value is that it makes the day-to-hour derivation explicit, so another reader can recompute every step. The table below gives the full twelve cells for a Xin day as a reference and leaves one blank row for you to fill with a different day stem.
Checking the derivation against the example chart
Wenbu's introductory guide gives a fixed teaching example: 2005-12-23 08:37, Asia/Shanghai, civil clock, midnight day boundary, no solar-time correction, with pillars Yi You, Wu Zi, Xin Si and Ren Chen. It is not a user profile but a reproducible teaching record, which makes it suitable for testing whether your five-rat derivation matches the tool.
Check in this order. First confirm the time falls in the Chen interval, 07:00 to before 09:00. Then take Xin from the day pillar Xin Si. Apply Bing-Xin days start at Wu Zi and count to Chen, which gives Ren Chen. Finally compare with the returned hour pillar, also Ren Chen. Agreement shows your derivation matches the calculation under these settings. If it does not, check time zone, day boundary and hour edges before doubting the rule.
Flag the late-Zi exception separately
The twelve-cell worksheet uses the ordinary five-rat starting rule, but Wenbu's default 00:00 day boundary treats 23:00–23:59 specially: the day pillar stays with the current day, while the hour stem follows the library's next-day convention. So for someone born at 23:30, deriving the Zi-hour stem from the current day stem by the plain rule may give a different hour stem than the tool returns. The rule is not wrong; the day-boundary convention is at work.
The fix is simple. For a late-Zi time, read the returned hour pillar first, or switch to the 23:00 Zi-start boundary and compare the two returned results, and mark that cell on the worksheet as a late-Zi case. The published notes also recommend comparing results under different settings near a day change or hour boundary. This is not a claim that one convention is correct; it is a reminder to record settings alongside the derivation.
Keep derivation separate from interpretation
Deriving an hour stem belongs to the calendar layer, which can be recomputed from a date, a time zone and stated rules. What an hour pillar means, and how to read it, belongs to the traditional symbolic layer. Wenbu's notes keep the two apart: a calculation can be reproduced by convention without its interpretation being scientifically validated. A successful worksheet check shows you can apply the lookup; it is not evidence for any prediction or for health or financial claims.
A second confusion treats the hour pillar as a complete description of a person. The guide notes that stem-branch combinations are finite and an hour pillar usually spans a two-hour interval, so identical symbols do not record someone's circumstances or choices. Treating the derivation as a checkable record rather than a conclusion is the more careful way to use the worksheet.
| Day stem | Zi to Si | Wu to Hai | Check point |
|---|---|---|---|
| Xin (filled) | Zi Wu, Chou Ji, Yin Geng, Mao Xin, Chen Ren, Si Gui | Wu Jia, Wei Yi, Shen Bing, You Ding, Xu Wu, Hai Ji | Chen cell is Ren Chen, matching the example chart |
| Jia-Ji (start reference) | Zi Jia, Chou Yi, Yin Bing, Mao Ding, Chen Wu, Si Ji | Wu Geng, Wei Xin, Shen Ren, You Gui, Xu Jia, Hai Yi | Jia-Ji days start at Jia Zi |
| Bing-Xin (start reference) | Zi Wu, Chou Ji, Yin Geng, Mao Xin, Chen Ren, Si Gui | Wu Jia, Wei Yi, Shen Bing, You Ding, Xu Wu, Hai Ji | Bing-Xin days start at Wu Zi |
| (your day stem) | Zi, Chou, Yin, Mao, Chen, Si | Wu, Wei, Shen, You, Xu, Hai | Fill the Zi cell first, then run in order |
Wenbu · BaZi guide ↗Wenbu · calculation conventions ↗
Hypothetical practice: twelve cells for a Xin day, checked against the example chart
The following is a hypothetical practice situation for demonstrating the worksheet; it does not describe any real person. Suppose you hold a record whose day stem is Xin and whose birth time falls in the Chen interval, and you want to derive the hour stem yourself before comparing with the returned example chart.
- First, apply the rule to the starting value: Bing-Xin days start at Wu Zi, so the Zi-hour stem is Wu.
- Second, run the sequence: Zi Wu, Chou Ji, Yin Geng, Mao Xin, Chen Ren, Si Gui, Wu Jia, Wei Yi, Shen Bing, You Ding, Xu Wu, Hai Ji.
- Third, confirm the interval: the example's 08:37 falls in Chen, 07:00 to before 09:00, so take the Chen cell and get Ren Chen.
- Fourth, compare with the chart Wenbu returns: pillars Yi You, Wu Zi, Xin Si and Ren Chen, day stem Xin, hour pillar Ren Chen, matching the derivation.
- Fifth, record the settings: civil clock, Asia/Shanghai, midnight day boundary, no solar-time correction, so another reader can recompute the same record. If the time were 23:30, the late-Zi exception would apply and this table could not be used directly.
The derivation matches the returned hour pillar, which shows you applied the five-rat rule correctly under these settings. It validates only the lookup process, not any reading of a person; with a different day boundary or solar-time setting, take the day stem again and redo the sequence.
Questions you may have
Must the hour stem always be derived with the five-rat rule?
The five-rat rule is a common traditional method that fixes the Zi-hour stem from the day stem and then runs the twelve hours in order. The ten day stems fall into five groups, each with one starting stem, and with the twelve branches these yield the sixty hour pillars, which makes hand-checking practical. Schools may differ on day-boundary and solar-time settings, but the rule itself is a lookup step, not a judgment about a person's fate.
Why does my hour stem differ from the tool's?
Compare inputs before doubting the rule: Gregorian date, local clock time, time zone, day-boundary setting and the true-solar-time option. Wenbu defaults to a 00:00 day change and also offers 23:00 Zi-start; enabling true solar time applies an approximate correction to the day and hour pillars. In particular, for 23:00–23:59 the default boundary keeps the current day pillar but takes the hour stem from the next-day convention, so read the returned hour stem or switch the boundary and compare both results.
Can I derive an hour pillar if the birth time is unknown?
Not reliably. Wenbu's published notes state that no hour pillar is generated when the birth time is unknown, and the year and month pillars are provisionally set to local noon with an uncertainty note. Without a time there is no hour interval, so there is no cell to fill; leave it blank rather than guessing an hour and applying the rule.
If the check matches, does that validate an interpretation?
No. A match shows only that you applied the lookup correctly under the given settings, which is the calendar layer. Wenbu separates calculation from interpretation: a calculation can be reproduced by convention without its interpretation being scientifically validated. Traditional meanings, inferences and your own circumstances should be kept apart.
Terms in this guide
- Five-rat rule
- A traditional lookup that fixes the stem paired with the Zi (rat) hour from the day stem, then assigns the remaining hour stems in sequence.
- Day stem
- The heavenly stem of the day pillar, also called the Day Master; it is the only input to the five-rat rule and the reference for Ten Gods relations.
- Hour interval
- The two-hour span assigned to each branch, such as Chen from 07:00 to before 09:00; the birth time determines which cell applies.
- Day-boundary setting
- The convention for when a day begins; Wenbu defaults to 00:00 and also offers a 23:00 Zi-start, which affects which day pillar a moment belongs to and the hour stem for late Zi.
See the claim and source notes
Wenbu's example chart lists the four pillars Yi You, Wu Zi, Xin Si and Ren Chen, with Xin as the day stem and Ren Chen as the hour pillar.
乙酉 / 戊子 / 辛巳 / 壬辰
The example's time falls in the Chen interval, running from 07:00 to before 09:00.
The time falls in the Chen interval, from 07:00 to before 09:00.
By default the day and hour pillars use the selected local clock time, so day-boundary and solar-time settings can change the result.
日、时柱默认使用所选当地钟表时间
Sources and review scope
Wenbu drafted and checked this article in Codex. The source list records the scope of the review.
- Wenbu · BaZi guide ↗Existing editorial and reproducible chart conventions · 2026-11-06 · Fetched text
- Wenbu · calculation conventions ↗First-party implementation; not evidence of predictive accuracy · 2026-11-06 · Fetched text
- lunar-typescript · official source ↗Calculation implementation and conventions · 2026-11-06 · Fetched text
Generate a chart from the example record and check your hour-stem derivation cell by cell
Enter 2005-12-23 08:37 with Asia/Shanghai in Wenbu's BaZi tool, keep the default day boundary and leave true solar time off, read the day stem, fill all twelve cells by the five-rat rule, then compare with the returned hour pillar; if they differ, check settings before redoing the sequence.
Generate a chart from the example record and check your hour-stem derivation cell by cell ↗If the copied hour pillar is Ren Chen and the chart used the ordinary Chen hour under a verified convention, the day stem can be Bing or Xin. Count back four stems from Ren to Wu. Both Bing and Xin start from Wu Zi in the Five Rats table, so both give Ren Chen at Chen. Use a trusted date or the original chart to choose between them.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
- Check the branch and the validity of the copied pair before reversing the rule.
- Step back from Ren to Wu and retain both Bing and Xin.
- Look up the date or the original day pillar to resolve the candidates.
Work back from the hour pillar
- 01Verify the hour
In this exercise, 08:37 belongs to Chen.
- 02Count back four
Go from Ren through Xin, Geng and Ji to Wu.
- 03Keep both day stems
Read Bing and Xin in the starting table, then seek independent date evidence.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Check the two copied characters before reversing the rule
Suppose the notebook lists 08:37 at the birthplace and Ren Chen, but the day pillar is missing. Check that the original chart used local civil time without solar correction and that it put the time in Chen. If another copy says Gui Si, check the original time, branch and settings. Gui Si can occur as a pair, but Si does not match the recorded hour under these settings.
Some transcriptions can be ruled out even without the clock. Gui Chen does not occur in the ordinary stem and branch pairing. Under the five starting rows in the worksheet, the possible stems at Chen are Jia, Bing, Wu, Geng and Ren. Keep the questionable copy and look for the source chart instead of quietly replacing a character.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Read the rule backwards and preserve both candidates
From Zi, the steps are Chou, Yin, Mao and Chen. Move back four places from Ren through Xin, Geng and Ji to Wu. The worksheet gives Bing and Xin as the two days that start at Wu Zi. A copied Yi day stem and a Ren Chen hour pillar cannot both fit this same ordinary daytime calculation. That mismatch is a reason to check the records.
For a direct calculation, use 08:37 and Asia/Shanghai. Set rollover to midnight and leave solar correction off. On April 2, 2024 the day pillar is Bing Shen. On April 7 it is Xin Chou. Both hour pillars are Ren Chen. On April 1 the day is Yi Wei and the hour is Geng Chen. These are three practice charts, each with its own known date.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
| Date or record | Day pillar | Hour pillar | What it shows |
|---|---|---|---|
| 2024-04-02 | Bing Shen | Ren Chen | Fits the Bing candidate |
| 2024-04-07 | Xin Chou | Ren Chen | Fits the Xin candidate |
| 2024-04-01 | Yi Wei | Geng Chen | Yi gives a different Chen-hour stem |
| Copied Gui Chen | Unknown | Gui Chen | Check the original transcription |
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Audit a fictional note that only gives Ren Chen
The fictional note also gives 08:37 and a verified civil-clock convention.
- Set Asia/Shanghai, midnight rollover and solar correction off for the exercise.
- Use the four steps from Chen back to Zi to find Wu Zi.
- Run April 2 and April 7. Read the two different day pillars and the shared Ren Chen hour pillar.
- If another line in the note says Yi, run April 1 to see the contrasting Geng Chen result.
Record Bing or Xin as the two possible day stems. Leave the day pillar open until you can verify the date.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Questions you may have
Can I get the entire day pillar from Ren Chen?
The reverse check returns two possible day stems. It supplies no day branch. An independently known date or the source chart is needed for the complete day pillar.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Can I use the same example at 23:30?
Check the late Zi rules in the original chart before applying the worksheet. The day and hour stems around rollover follow the stated convention, which is outside this daytime example.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
What should I change first if the clock and branch disagree?
Keep the original note. Check the chart's clock convention, time zone, correction settings and column labels. Leave the reverse check unresolved while those inputs remain uncertain.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Terms in this guide
- Zi starting stem
- The stem assigned to Zi for a particular day-stem group. The next stems can be counted forward from it.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
- Day-stem group
- The pair of day stems that share one starting stem under the Five Rats rule.
Current complete en canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
See the claim and source notes
Bing and Xin share the Wu Zi starting pair in the existing worksheet.
Bing-Xin days start at Wu Zi
The beginner guide gives Xin Si as the day pillar and Ren Chen as the hour pillar in one example.
Xin Si and Ren Chen
The public method calls for checking settings near boundaries. The worked example keeps its ordinary daytime input fixed.
临近换日或时辰边界时
Sources and review scope
Wenbu drafted and checked this article in Codex. The source list records the scope of the review.
- Current complete zh canonical article ↗Current public original and earlier additions; add substantial coverage without repeating or replacing them. · 2026-11-13 · Fetched text
- Current complete en canonical article ↗Current public original and earlier additions; add substantial coverage without repeating or replacing them. · 2026-11-13 · Fetched text
- Wenbu · calculation conventions ↗First-party implementation; not evidence of predictive accuracy · 2026-11-13 · Fetched text
- Wenbu · BaZi guide ↗Existing editorial and reproducible chart conventions · 2026-11-13 · Fetched text
- lunar-typescript · official source ↗Calculation implementation and conventions · 2026-11-13 · Fetched text
Compare the Bing and Xin examples in the BaZi tool
Run both dates with the same settings. Read the top character of the day pillar and then compare the complete hour pillars.
Compare the Bing and Xin examples in the BaZi tool ↗