When the birth year carries a 乙 (Yǐ) heavenly stem, the twelve month stems are set before you even look at the calendar. This is the bazi month stem table for yi year charts, and it comes straight from the Five Tigers rule (五虎遁 wǔhǔdùn): a 乙 year opens its first month on 戊 (Wù), then each month advances one stem through the cycle. Here is the full year, month by month.
The 12 month pillars for a Yi 乙 year
Months turn at a major solar term (節 jié), never on the first of a calendar month. Locate your birth branch and read across to the pillar.
| Month | Branch | Starts at (solar term) | Month pillar |
|---|---|---|---|
| 1st | Tiger 寅 Yín | Li Chun 立春 (~4 Feb) | 戊寅 Wù Yín |
| 2nd | Rabbit 卯 Mǎo | Jing Zhe 惊蛰 (~6 Mar) | 己卯 Jǐ Mǎo |
| 3rd | Dragon 辰 Chén | Qing Ming 清明 (~5 Apr) | 庚辰 Gēng Chén |
| 4th | Snake 巳 Sì | Li Xia 立夏 (~5 May) | 辛巳 Xīn Sì |
| 5th | Horse 午 Wǔ | Mang Zhong 芒种 (~6 Jun) | 壬午 Rén Wǔ |
| 6th | Goat 未 Wèi | Xiao Shu 小暑 (~7 Jul) | 癸未 Guǐ Wèi |
| 7th | Monkey 申 Shēn | Li Qiu 立秋 (~7 Aug) | 甲申 Jiǎ Shēn |
| 8th | Rooster 酉 Yǒu | Bai Lu 白露 (~7 Sep) | 乙酉 Yǐ Yǒu |
| 9th | Dog 戌 Xū | Han Lu 寒露 (~8 Oct) | 丙戌 Bǐng Xū |
| 10th | Pig 亥 Hài | Li Dong 立冬 (~7 Nov) | 丁亥 Dīng Hài |
| 11th | Rat 子 Zǐ | Da Xue 大雪 (~7 Dec) | 戊子 Wù Zǐ |
| 12th | Ox 丑 Chǒu | Xiao Han 小寒 (~5 Jan) | 己丑 Jǐ Chǒu |
A 乙 year opens on 戊 earth and reaches its own stem 乙 in the eighth month, the Rooster. That 乙酉 in the middle of autumn is the fingerprint of the Yǐ column.
Which years take this column
Calendar years ending in 5 carry the 乙 stem: 1985, 1995, 2005, 2015, 2025. The caveat, as always, is Li Chun (立春 lìchūn) around 4 February — the Ba Zi year turns at that solar term, not at 1 January and not at Chinese New Year. January births in a calendar 乙 year still belong to the previous 甲 year and read from the Jia-year column; conversely, January births of the following calendar year usually still count as 乙 and stay on this table.
A worked example
Consider a birth in the Rooster month (酉 Yǒu) of a 乙 year. The eighth row gives 乙酉 (Yǐ Yǒu): a 乙 wood stem on a 酉 metal branch, wood sitting directly over the metal that cuts it. The Rooster month begins at Bai Lu (白露 báilù) around 7 September, so a birth on, say, 5 September of that year has not yet crossed into the Rooster and still belongs to the Monkey month, making the pillar 甲申 (Jiǎ Shēn). Two days on the calendar, an entirely different month pillar. That is why the solar term, not the date, must be checked first. The Rooster month page and the Monkey month page unpack what each of those branches then does to the chart.
The rule behind the rows
Stated in full, the Five Tigers mechanic runs: first-month (寅) stem index = (year-stem-index mod 5) × 2 + 2; each later month adds 1, mod 10. Year stems pair: 甲/己, 乙/庚, 丙/辛, 丁/壬, 戊/癸 share columns. With the stems numbered 甲 0 through 癸 9, a 乙 year has index 1, so (1 mod 5) × 2 + 2 = 4 — stem number 4 is 戊, and the Tiger month duly opens on 戊寅. Every later row just counts one stem forward. Knowing the mechanic means you can rebuild the table from memory instead of trusting a screenshot.
What the month pillar governs
The month pillar holds the month palace, which a practitioner reads for career climate and for the parental line. Beyond that surface, the month branch carries the ruling element of the season, and the season is the strongest single vote on whether the chart runs hot or cold. This is why the month branch weighs so heavily when we judge a strong or weak Day Master: a Day Master born into its own supporting season starts with the wind at its back. In a 乙 year the month stems move through metal and water in the second half, which shapes how much pressure or support the season actually delivers.
Season, here, means the solar-term season the branch belongs to — spring 寅卯辰, summer 巳午未, autumn 申酉戌, winter 亥子丑 — and each one grades a Day Master through the five states (旺相休囚死 wàng xiàng xiū qiú sǐ). The 乙酉 signature month is a sharp illustration: a Yi Wood Day Master born there sits in Metal’s own season, the grade classical texts call Dormant, a position examined in detail in Yi Wood born in autumn.
Reading it in context
Take the month stem as an opening move, not a conclusion; it interacts with hidden stems in the branch and with the rest of the chart. Under the Five Tigers rule, 乙 and 庚 (Gēng) years share this column, so the month table for Geng 庚 years matches this one line for line. For the full five-column grid see the master month stem table, and for what the branch itself conceals, the stems and branches alphabet lays out the hidden stems.
Common questions on the Yi column
Why does the table start on 戊 rather than 乙?
The first month’s stem is generated from the year stem by the formula above, not copied from it. Only two columns happen to open on their own stem family; 乙 is not one of them, and its own stem does not surface until the Rooster month.
My birthday is 4 February 1985. Which table applies?
Whichever side of the exact Li Chun moment your birth time falls on — that year the boundary sits close to the date itself. This is precisely the case where reading a table by date fails and only the exact term time, as the calculator applies it, settles both year and month.
Does the month stem alone make my Day Master strong or weak?
No. The branch and its season do most of that work; the stem colours the month palace and adds one visible character to the count. Strength is judged on the whole chart, never on one stem.
Check your own Yi-year month pillar against the exact solar-term boundary — plot your full chart free with the Butcher Boy calculator and read it back against the table above.