The BaZi Month Pillar: Solar Terms Set the Branch, the Five Tigers Set the Stem
The month pillar holds the month branch, the most important single position in the chart, and it is also the pillar people get wrong most often. The reason is simple: a BaZi month is neither a Gregorian month nor a lunar month but a solar-term month.
Step one: the solar term gives the branch
| Jie term | Month branch | Approximate date (Gregorian) |
|---|---|---|
| Start of Spring (立春) | Yin (寅) | Around Feb 4 |
| Awakening of Insects (驚蟄) | Mao (卯) | Around Mar 6 |
| Pure Brightness (清明) | Chen (辰) | Around Apr 5 |
| Start of Summer (立夏) | Si (巳) | Around May 6 |
| Grain in Ear (芒種) | Wu (午) | Around Jun 6 |
| Minor Heat (小暑) | Wei (未) | Around Jul 7 |
| Start of Autumn (立秋) | Shen (申) | Around Aug 8 |
| White Dew (白露) | You (酉) | Around Sep 8 |
| Cold Dew (寒露) | Xu (戌) | Around Oct 8 |
| Start of Winter (立冬) | Hai (亥) | Around Nov 7 |
| Major Snow (大雪) | Zi (子) | Around Dec 7 |
| Minor Cold (小寒) | Chou (丑) | Around Jan 6 |
Only the jie (節) terms count, not the middle terms (Rain Water, the Spring Equinox and so on). And it is the exact moment that counts: if you were born on the day a term changes, it matters whether you were born before or after it; see solar term boundaries.
Step two: the Five Tigers rule gives the stem
Five Tigers (五虎遁, wu hu dun): from the year stem to the Yin month stem
甲己之年丙作首，乙庚之歲戊為頭，丙辛必定尋庚起，丁壬壬位順行流，更有戊癸何方覓，甲寅之上好追求。
The "tiger" is the Yin (寅) month, the first month of the BaZi year. The verse names the stem that month takes in each kind of year: in a Jia or Ji year the Yin month begins with Bing; Yi or Geng, with Wu; Bing or Xin, with Geng; Ding or Ren, with Ren; Wu or Gui, with Jia.
In other words, a Jia or Ji year has a Bing-Yin month, a Yi or Geng year a Wu-Yin month, and so on. Once you have the Yin month's stem, each month after it (Mao, Chen…) moves the stem on by one.
| Year stem | Yin 寅 | Mao 卯 | Chen 辰 | Si 巳 | Wu 午 | Wei 未 | Shen 申 | You 酉 | Xu 戌 | Hai 亥 | Zi 子 | Chou 丑 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Jia or Ji year 甲、己 | 丙寅 Bing-Yin | 丁卯 Ding-Mao | 戊辰 Wu-Chen | 己巳 Ji-Si | 庚午 Geng-Wu | 辛未 Xin-Wei | 壬申 Ren-Shen | 癸酉 Gui-You | 甲戌 Jia-Xu | 乙亥 Yi-Hai | 丙子 Bing-Zi | 丁丑 Ding-Chou |
| Yi or Geng year 乙、庚 | 戊寅 Wu-Yin | 己卯 Ji-Mao | 庚辰 Geng-Chen | 辛巳 Xin-Si | 壬午 Ren-Wu | 癸未 Gui-Wei | 甲申 Jia-Shen | 乙酉 Yi-You | 丙戌 Bing-Xu | 丁亥 Ding-Hai | 戊子 Wu-Zi | 己丑 Ji-Chou |
| Bing or Xin year 丙、辛 | 庚寅 Geng-Yin | 辛卯 Xin-Mao | 壬辰 Ren-Chen | 癸巳 Gui-Si | 甲午 Jia-Wu | 乙未 Yi-Wei | 丙申 Bing-Shen | 丁酉 Ding-You | 戊戌 Wu-Xu | 己亥 Ji-Hai | 庚子 Geng-Zi | 辛丑 Xin-Chou |
| Ding or Ren year 丁、壬 | 壬寅 Ren-Yin | 癸卯 Gui-Mao | 甲辰 Jia-Chen | 乙巳 Yi-Si | 丙午 Bing-Wu | 丁未 Ding-Wei | 戊申 Wu-Shen | 己酉 Ji-You | 庚戌 Geng-Xu | 辛亥 Xin-Hai | 壬子 Ren-Zi | 癸丑 Gui-Chou |
| Wu or Gui year 戊、癸 | 甲寅 Jia-Yin | 乙卯 Yi-Mao | 丙辰 Bing-Chen | 丁巳 Ding-Si | 戊午 Wu-Wu | 己未 Ji-Wei | 庚申 Geng-Shen | 辛酉 Xin-You | 壬戌 Ren-Xu | 癸亥 Gui-Hai | 甲子 Jia-Zi | 乙丑 Yi-Chou |
Generated by our engine. Note: use the year stem after the Start of Spring rule is applied, so someone born in January uses the previous year's stem.
Worked example: March 12, 1985, You hour
Born March 12, 1985 (Gregorian), 5–7 p.m.
- ① Year pillar: in 1985 the Start of Spring fell at 1985-02-04 05:11; March 12 is after it, so use 1985. (1985 − 4) ÷ 10 leaves 1 → stem number 2, Yi (乙); ÷ 12 leaves 1 → branch number 2, Chou (丑). Year pillar: Yi-Chou (乙丑).
- ② Month pillar: the last jie term before the birth was the Awakening of Insects (1985-03-05 23:16), so the month branch is Mao. For a Yi year the Five Tigers verse says "in Yi and Geng years, Wu leads," so the Yin month is Wu-Yin; count 1 on to Mao, and the month pillar is Ji-Mao (己卯).
- ③ Day pillar: January 1, 2000 was Wu-Wu (number 55, index 54). March 12, 1985 is 5408 days earlier: (54 − 5408) divided by 60 leaves 46, which is number 47, so the day pillar is Geng-Xu (庚戌).
- ④ Hour pillar: for a Geng day the Five Rats verse says "Yi and Geng begin with Bing," so the Zi hour is Bing-Zi; count 9 on to You, and the hour pillar is Yi-You (乙酉).
Watch your chart being worked out, step by step
Enter your Gregorian birthday and hour. The tool follows the method on this page and shows how each of the year, month, day and hour pillars is calculated, then checks the result against our chart engine. Everything is calculated in your browser; nothing is uploaded.
Uses your Gregorian birthday, with the day changing at 11 p.m.; the solar terms are compared at the middle of your two-hour period (as in our main chart calculator).
A straight word: working it by hand is for understanding, not for replacing a calculator
Once you have worked a chart by hand, you know where every character in it comes from, and you can read other people's charts with more confidence. Real charts, though, turn on the exact moment of a solar term, daylight saving time and true solar time, and one slip costs you a whole pillar. When you are done, check it once with a calculator. Everything on this site is for reference and entertainment.
Work out your month pillar
Enter your birthday, and the tool finds the last jie term before your birth and works out the month pillar with the Five Tigers rule.
Month pillar FAQ
How do you calculate the BaZi month pillar?
The branch follows the solar terms (the Start of Spring begins the Yin month, the Awakening of Insects the Mao month…); the stem comes from the Five Tigers rule, which gives the Yin month stem from the year stem, and then moves on one step per month.
Does the month pillar follow the lunar month?
No. It follows the solar terms. Someone born in the first days of the first lunar month may not yet have reached the Start of Spring and is still in the Chou month.
What is the Five Tigers verse?
The verse (甲己之年丙作首，乙庚之歲戊為頭，丙辛必定尋庚起，丁壬壬位順行流，更有戊癸何方覓，甲寅之上好追求。) says: in a Jia or Ji year the Yin month begins with Bing; Yi or Geng, with Wu; Bing or Xin, with Geng; Ding or Ren, with Ren; Wu or Gui, with Jia.