What the month command is: identify the month branch before discussing season
In BaZi, the month command usually means the earthly branch of the month pillar — the branch of the solar-term month in which the birth instant falls. To identify it, fix four things first: the Gregorian birth date (if the original record is lunar, verify the leap month and convert only once), the local clock time with its IANA time-zone name, the absolute instant obtained from date plus time plus zone, and which two “jie” terms bracket that instant. Wenbu's methodology states that the year and month pillars are compared against solar-term times using the birth's absolute instant, with a fixed UTC+08:00 standard time and no historical daylight saving; the day and hour pillars default to the selected local clock time. So the month branch is not a direct translation of “December means Zi month,” nor can it be read off the lunar month. Only after the branch is fixed does the question “what does this season mean for the chart” arise — and that belongs to interpretation, which must name its school or rule set rather than being folded into the calendar result.
Wenbu · BaZi guide ↗Wenbu · calculation conventions ↗Hong Kong Observatory · calendar conversion ↗
- Treat the month command first as a locatable position: which solar-term month contains the birth instant.
- The month branch is set by solar-term boundaries, not by the Gregorian or lunar month number.
- “Whether this season supports or drains the chart” is interpretation and must name its school.
- Recording date, time, zone, solar term, branch and claim type on one line lets another reader check your work.
Five steps from birth record to month branch
- 01Fix the birth date and instant
Write the Gregorian birth date, the local clock time and the IANA time-zone name, then convert all three into an absolute instant; do not subtract hours yourself while still selecting the original zone.
- 02Find the opening jie
In a solar-term table, locate the most recent “jie” before the birth instant and note its time.
- 03Compare the order
If the birth instant is after that jie and before the next one, the month branch is the one opened by that jie.
- 04Flag boundary risk
If the birth time is only minutes from a month change, note the uncertainty instead of forcing a single branch.
- 05Split the claims
Put calendar-settled items in one column; put seasonal strength, structure or favorable-element judgments in another, with the school named.
Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗Hong Kong Observatory · calendar conversion ↗
What the month command names: position versus meaning
In the four pillars, the month pillar is one heavenly stem plus one earthly branch, and the month command usually refers to that branch. It marks the solar-term month interval containing the birth instant — a positional label, not a personality verdict. Wenbu's introductory guide splits the chart into four stem-branch pairs for year, month, day and hour, and asks readers to check the birth record and calculation conventions before moving to interpretation; identifying the month branch belongs to that first step.
It matters that the same branch can carry different seasonal meanings and uses across schools. Some discuss strength, some discuss climate adjustment, some look only at the branch's relation to the Day Master. These are interpretive layers and are not equivalent. This article settles only which branch applies and which solar term opened it; it does not decide for any school.
Solar-term month changes: where the boundary sits
Traditional BaZi changes months at the “jie” terms, not at the first day of a lunar month. Wenbu's methodology says the year and month pillars are compared against solar-term times using the birth's absolute instant, with fixed UTC+08:00 standard time and no historical daylight saving; the day and hour pillars default to the selected local clock time. In other words, the month branch depends on the order of the absolute instant relative to the solar-term instant, not on the clock reading in your city by itself.
Be careful near the boundary. The Hong Kong Observatory's conversion table notes that uncertainty in solar-term times decades ahead may reach a few minutes, and if a term falls close to midnight the tabulated date may differ by one day. So when a birth time sits minutes from a month change, the honest record says “near the boundary, uncertain” rather than reporting one confident branch. If true solar time correction is enabled, Wenbu still computes the year and month pillars from the original absolute instant, and that setting should be noted too.
Wenbu · calculation conventions ↗Hong Kong Observatory · calendar conversion ↗Wenbu · BaZi guide ↗
A one-record worksheet
The worksheet needs only one row, but every cell must be traceable. Cell one: the Gregorian birth date, noting whether the original record was lunar and whether one conversion was made. Cell two: local clock time plus IANA time-zone name, converted through date, time and zone into an absolute instant. Cell three: the most recent “jie” before that instant, with its time. Cell four: the resulting month branch. Cell five: the claim type — settled by the calendar, or interpretation that must name a school. Cell five is the one people get wrong, because it forces you to admit which rule set you are quoting.
Two mistakes recur. First, treating the lunar month as the month branch and ignoring the solar-term boundary; that is a calendar error. Second, treating “born in month X, therefore season Y” as a chart judgment; that is a level confusion. Putting these in separate cells makes it harder to blend checkable fact with debatable interpretation when you later review the record or discuss it with someone else.
From month branch to seasonal reading: say what you mean
Only after the branch is confirmed does seasonal influence come up. At that point, write down which school and which rule you are using and what judgment follows, such as “this element is relatively strong in this season.” Wenbu's element diagram counts each visible stem and branch once to show occurrences; it adds no hidden-stem weighting or seasonal influence, so counts alone cannot establish strength, structure or a favorable element. That is exactly the point: counting and seasonal interpretation are separate operations.
If two charts disagree, compare inputs and calculation rules before comparing prose. For the month branch, the key is whether the birth date, clock time, time zone and solar-term instant match; the day-boundary rule and true solar time correction affect the day and hour pillars, so note them in the record but do not describe them as changing the month branch. This article offers no strength score and no remedies, because those require an explicit school premise and go beyond identifying the branch.
| Item | Determined by | Reproducible? | How this article handles it |
|---|---|---|---|
| Birth date and absolute instant | Gregorian date plus clock time plus zone conversion | Yes, recompute in the same zone | Worksheet cells one and two |
| Opening jie | Solar-term time table | Yes, but far-future terms carry minutes of uncertainty | Cell three, with boundary risk noted |
| Month pillar branch | Order of birth instant versus solar-term instant | Yes, under the same rule | Cell four |
| Seasonal strength judgment | The school and rule adopted | Only if the premise is stated | Separate column, school named, no score |
| Element occurrence count | Each visible stem and branch counted once | Yes, under the same counting method | Recorded apart from seasonal reading |
Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗Hong Kong Observatory · calendar conversion ↗
Hypothetical case: a month branch near the boundary
The following is a teaching scenario, not real personal data and not a computed chart. Suppose a birth record reads “21 December, clock time 23:58, time zone UTC+08:00,” and the person was told a “jie” fell near midnight that night. The task is not to guess a fate but to complete the worksheet row.
- Step one: write the Gregorian date 21 December, the clock time 23:58 and the time-zone name, convert all three to an absolute instant, and note that true solar time correction was not applied.
- Step two: look up the jie time in a solar-term table and find it very close to midnight, where far-future terms carry minutes of uncertainty.
- Step three: compare the order. If the birth instant precedes the jie, the branch belongs to the previous solar-term month; if it follows, it belongs to the new one. Write both possibilities.
- Step four: in the conclusion cell, write “near the boundary, two possible month branches,” and list the branch name for each case rather than only one.
- Step five: in a separate column, note that any seasonal-strength discussion must name its school and rule; this article draws no strength conclusion.
What this exercise teaches is that identifying the month branch is a checking process that can legitimately record two possible answers, rather than a demand for one immediate verdict. Writing the date, time, zone and uncertainty into the record is more useful than forcing certainty, and it preserves a traceable premise for any later interpretation.
Wenbu · calculation conventions ↗Hong Kong Observatory · calendar conversion ↗Wenbu · BaZi guide ↗
Questions you may have
Is the month branch just the earthly branch of the lunar month?
No. BaZi typically changes months at the “jie” terms rather than at the first day of a lunar month, so lunar months and month branches do not map one-to-one. Confirm the Gregorian birth date and clock time, convert to an absolute instant, compare it with solar-term times to find the solar-term month, then read the branch.
What if the birth time falls minutes from a month change?
Record it as “near the boundary, uncertain.” The Hong Kong Observatory notes that far-future solar-term times may be uncertain by a few minutes, and near midnight the tabulated date may differ by a day. Listing two possible branches is more honest than forcing one.
Hong Kong Observatory · calendar conversion ↗Wenbu · calculation conventions ↗
Once the month branch is confirmed, can I judge chart strength directly?
Not directly. The branch is a positional label; strength, structure and favorable elements are interpretive and need a named school and rule. Wenbu's element diagram counts visible characters only, with no seasonal weighting, so counts alone cannot establish strength.
Does enabling true solar time correction change the month branch?
Per Wenbu's methodology, true solar time correction applies to the day and hour pillars using longitude and equation-of-time approximations, while the year and month pillars still use the original absolute instant. The branch basis is unchanged, but note in the record whether the correction was on.
Terms in this guide
- Month command
- Usually the earthly branch of the month pillar, marking the solar-term month interval containing the birth instant; a positional label, not a personality verdict.
- Jie
- The solar-term nodes used for month changes in BaZi, as opposed to the first day of a lunar month.
- Absolute instant
- The unified time basis obtained by converting the Gregorian birth date and local clock time through their time zone, used for comparison with solar-term times.
- Boundary uncertainty
- When a birth time sits very close to a month change, minutes of error in the solar-term time can leave two possible month branches.
Hong Kong Observatory · calendar conversion ↗Wenbu · calculation conventions ↗
See the claim and source notes
BaZi typically changes months at the relevant jie terms rather than at Lunar New Year.
changes months at the relevant jie terms
Wenbu compares the year and month pillars against solar-term times using the absolute instant.
年、月柱按出生绝对时刻与节气时刻比较
Solar-term times carry calculation uncertainty, and near midnight the date may differ by a day.
may have a discrepancy of one day
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 · 2026-11-07 · Fetched text
- Wenbu · calculation conventions ↗First-party implementation; not evidence of predictive accuracy · 2026-11-07 · Fetched text
- Hong Kong Observatory · calendar conversion ↗Official calendar reference; not evidence of fortune-telling · 2026-11-07 · Fetched text
Generate a chart in Wenbu and check the month pillar branch
Enter the Gregorian birth date, clock time and time zone in Wenbu's BaZi tool, read the month pillar branch, and record the solar-term boundary and claim type on this worksheet; that completes identification only, not a strength judgment.
Generate a chart in Wenbu and check the month pillar branch ↗Can two different month pillars have the same month branch?
Yes. The month pillars 壬申 (Ren Shen) and 甲申 (Jia Shen) share the branch 申 (Shen). In this guide, the month command refers to that branch. Ren and Jia are different month stems, so the full pillars differ. Find the month column, copy both characters, and compare the second one. The two charts below also show how easy it is to copy the year branch by mistake.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
- Compare the second character of each month pillar for the branch.
- Compare both characters for the full pillar.
- Keep the column label with each copied value.
Three fields for checking two charts
- 01Locate the column
Copy the two characters under Month and retain the column name.
- 02Split the pair
First character: stem. Second: branch. For 甲申 they are Jia and Shen.
- 03Name the match
Both branches are Shen. The different stems make the full pillars different.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Split the two characters before you compare
Use three fields: full month pillar, month stem and month branch. Ren Shen splits into Ren and Shen; Jia Shen splits into Jia and Shen. The pairs differ, while the branch matches. Write which field you compared so both observations are clear.
In calculation data, find the pillar marked month and read its branch. On screen, start under the month heading. If a year and month branch happen to match, copying from the wrong column may go unnoticed until you check a second chart.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Use the second year to expose the copying error
Use August 20 at noon in Shanghai in 2004 and again in 2005. Set the day boundary to midnight and leave solar time off. A has year 甲申 and month 壬申; B has year 乙酉 and month 甲申. The year branches differ, while the month branches are both Shen.
If your notes give B a You month branch, check the column. You is the year branch here. If the note says the month pillars match, narrow it to the month branches. Both edits can be verified against the chart.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
| Field | A: 2004-08-20 | B: 2005-08-20 |
|---|---|---|
| Zone and clock | Asia/Shanghai, 12:00 | Asia/Shanghai, 12:00 |
| Year pillar for checking the column | 甲申 Jia Shen | 乙酉 Yi You |
| Full month pillar | 壬申 Ren Shen | 甲申 Jia Shen |
| Month stem and branch | 壬 Ren, 申 Shen | 甲 Jia, 申 Shen |
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Try it: which column did the note use?
A note says, “A has a Shen month; B has a You month.” Check it against the two fictional charts.
- Mark B’s month pillar 甲申, next to its year pillar 乙酉.
- Compare the second character of each month pillar. Both end in 申.
- Write: “The year branches are Shen and You. The month branches match, but the month stems differ.”
Keep the column labels in your notes so you can trace each value back to the chart.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Questions you may have
If the month branches match, can I merge the month pillars?
Keep the full pairs as two records. The branch can be a grouping field, but you still need Ren Shen and Jia Shen to reproduce the individual comparison.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Can I identify the month from 甲申 alone?
You need the column label. Here 甲申 is A’s year pillar and B’s month pillar. If a note has only the pair, find the original chart before assigning a month branch.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
Terms in this guide
- Month branch
- The second character of the month pillar. This guide records it as the month-command label.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
- Full month pillar
- The month stem and branch together, as in 壬申.
Current complete zh canonical article ↗Wenbu · calculation conventions ↗Wenbu · BaZi guide ↗
See the claim and source notes
The month pillar has a stem and a branch; this guide uses the branch for the month command.
月柱由一个月干和一个地支组成，月令通常就指这个月支
Wenbu determines year and month by comparing the birth instant with solar-term instants.
年、月柱按出生绝对时刻与节气时刻比较
The calculator separates the year, month, day and hour columns.
four columns show year, month, day and hour
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. · 2026-11-12 · Fetched text
- Current complete en canonical article ↗Current public original and earlier additions; add substantial coverage without repeating or replacing them. · 2026-11-12 · Fetched text
- Wenbu · BaZi guide ↗Existing editorial and reproducible chart conventions · 2026-11-12 · Fetched text
- Wenbu · calculation conventions ↗First-party implementation; not evidence of predictive accuracy · 2026-11-12 · Fetched text
- Wenbu · birth time and time zones ↗Existing editorial and boundary examples · 2026-11-12 · Fetched text
Compare the month columns in the BaZi calculator
Use the two dates and noon times in the table. Keep the Shanghai time zone and the same settings, then record the year and month columns.
Compare the month columns in the BaZi calculator ↗In Wenbu’s BaZi convention, Insects Waken opens the Mao month, and Rain Water falls within the preceding Yin month. In the 2025 examples, the month pillar is Wu Yin 戊寅 on both sides of Rain Water. The samples before and after Insects Waken give Wu Yin 戊寅 and Ji Mao 己卯 respectively. Compare your record with the opening jie of the month.
Wenbu · calculation conventions ↗Hong Kong Observatory · calendar conversion ↗Wenbu · versioned public capabilities ↗lunar-typescript · official source ↗
- Read the solar term’s category in the calendar. Rain Water is a middle term. Insects Waken is a month-opening jie.
- Keep the zone with the almanac time. Shanghai and Hong Kong use UTC+08:00 for the dates in this exercise.
- Check the two characters in the Month field. Record the stem and branch before writing which pair changed.
Check the two terms against the month pillar
- 01Record the almanac times
Rain Water is February 18 at 18:07. Insects Waken is March 5 at 16:07.
- 02Choose two sides
Keep the Gregorian date and use the same UTC+08:00 clock for these dates.
- 03Read the Month field
Both Rain Water rows are Wu Yin. Ji Mao appears after Insects Waken.
Wenbu · calculation conventions ↗Hong Kong Observatory · calendar conversion ↗Wenbu · versioned public capabilities ↗lunar-typescript · official source ↗
Find the two times in the almanac
Find the Solar Terms column on the February 2025 page of the Hong Kong Observatory Almanac. It gives Spring Showers, also called Rain Water, on February 18 at 18:07. The March page gives Insects Waken on March 5 at 16:07. Both use the Hong Kong clock. The Observatory’s 24 Solar Terms table classifies Rain Water as zhongqi (major) and Insects Waken as jie (minor).
The latest month-opening jie sets the branch in this BaZi convention. Rain Water falls during the Yin month that opened at Li Chun. Insects Waken opens Mao. Write down the name, time and category of each term before deciding where Month should change.
Wenbu · calculation conventions ↗Hong Kong Observatory · calendar conversion ↗Wenbu · versioned public capabilities ↗lunar-typescript · official source ↗
Keep the same location and compare the Month field
Use Asia/Shanghai, local civil time and the midnight day boundary. Enter the four Gregorian dates and times below and copy the Month field each time. February 18 gives Wu Yin twice. March 5 gives Wu Yin and then Ji Mao. The year pillar is Yi Si 乙巳 in all four results, a useful check that you copied from the month column.
The almanac displays times to the minute, and each test input is more than ten minutes from the printed time. If your record gives a time range, check whether that range spans the opening term before assigning one month pillar.
Wenbu · calculation conventions ↗Wenbu · versioned public capabilities ↗Current complete en canonical article ↗
| Date and local time | Relative to the solar term | Month pillar |
|---|---|---|
| 2025-02-18 17:55 | Before Rain Water | Wu Yin 戊寅 |
| 2025-02-18 18:20 | After Rain Water | Wu Yin 戊寅 |
| 2025-03-05 15:55 | Before Insects Waken | Wu Yin 戊寅 |
| 2025-03-05 16:20 | After Insects Waken | Ji Mao 己卯 |
Wenbu · calculation conventions ↗Wenbu · versioned public capabilities ↗Current complete en canonical article ↗
Test a note that puts Mao at Rain Water
Imagine a practice note that says the next chart should show Mao because Rain Water has already passed. Check it against four fixed inputs.
- Find both printed times in the almanac and align their zone with the chart inputs. For this example the clocks agree.
- Enter the February 18 pair. Both show Wu Yin. Record that the month is still Yin after Rain Water.
- Enter both March 5 times. Record Wu Yin for the first and Ji Mao for the second. Keep the Shanghai zone and local civil time with both entries.
- Keep the four results on the same worksheet. Put any seasonal interpretation in a separate note.
The February results match, and the March results differ. Record Insects Waken as the opening term in this comparison.
Wenbu · calculation conventions ↗Hong Kong Observatory · calendar conversion ↗Wenbu · versioned public capabilities ↗lunar-typescript · official source ↗
Questions you may have
Does a calendar’s major solar term change the BaZi month pillar?
Rain Water is the zhongqi in this pair, and the test gives Wu Yin on either side. Find the jie that opens the month under your calculator’s convention.
Wenbu · calculation conventions ↗Wenbu · versioned public capabilities ↗Current complete en canonical article ↗
Can the date alone settle the month pillar on Insects Waken?
Here 15:55 and 16:20 give different results on the same date. Check the original clock time and location. If the precision spans the dividing time, keep the possible periods and their results.
Wenbu · calculation conventions ↗Hong Kong Observatory · calendar conversion ↗Wenbu · versioned public capabilities ↗lunar-typescript · official source ↗
Terms in this guide
- Month-opening jie
- The solar-term instant that starts a BaZi month under this convention. Insects Waken opens Mao in the example.
Wenbu · calculation conventions ↗Wenbu · versioned public capabilities ↗Current complete en canonical article ↗
- Middle solar term
- A term in the zhongqi group, alternating with the twelve jie. Rain Water belongs to this group.
Hong Kong Observatory · calendar conversion ↗Current complete en canonical article ↗
See the claim and source notes
The existing guide describes the opening jie as the BaZi month boundary.
Traditional BaZi changes months at the “jie” terms
Wenbu compares the recorded instant with the solar-term instant to find the year and month pillars.
年、月柱按出生绝对时刻与节气时刻比较
Wenbu compares absolute solar-term instants in fixed UTC+08:00.
Absolute solar-term boundaries in fixed UTC+08:00
The Hong Kong Observatory offers Gregorian and lunar date tables by year.
Gregorian-Lunar Calendar Conversion Table
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. · 2026-11-14 · Fetched text
- Current complete en canonical article ↗Current public original and earlier additions; add substantial coverage without repeating or replacing them. · 2026-11-14 · Fetched text
- Wenbu · calculation conventions ↗First-party implementation; not evidence of predictive accuracy · 2026-11-14 · Fetched text
- Hong Kong Observatory · calendar conversion ↗Official calendar reference; not evidence of fortune-telling · 2026-11-14 · Fetched text
- Wenbu · versioned public capabilities ↗First-party current tool, convention and privacy contract; not external endorsement or predictive validation · 2026-11-14 · Fetched text
- lunar-typescript · official source ↗Calculation implementation and conventions · 2026-11-14 · Fetched text
Check these four times in the BaZi tool
Keep the Shanghai time zone and local civil time fixed, then copy both characters from the Month field.
Check these four times in the BaZi tool ↗