乙巳 Day Pillar — Yi Yin Wood Day Master (si Snake)
The yi si (乙巳) day pillar means you are a Yi Yin Wood day master sitting on the si (Snake, 火) branch. Its nayin is Lamp Fire (覆灯火). Below: what the stem says, what the branch adds, and how the pair interacts.
The 乙巳 day pillar at a glance
| Position in the cycle | No. 9 of the 60 day pillars |
|---|---|
| Day master (heavenly stem) | 乙 — Yi Yin Wood (Wood) |
| Day branch (earthly branch) | 巳 — si, the Snake (Fire) |
| Hidden stems | 丙 (Bing Fire), 庚 (Geng Metal), 戊 (Wu Earth) |
| Nayin | Lamp Fire (覆灯火) |
| Stem–branch relation | the stem drains into the branch |
What the day pillar means in BaZi
In the Four Pillars of Destiny (BaZi), the day pillar is the pillar of the self: its heavenly stem is your day master, the element that represents you, and its earthly branch is the ground you stand on, closest to your inner life and (traditionally) your marriage palace. All other pillars are read in relation to the day stem. That is why the 60 day pillars are the most-asked-about combinations in Chinese astrology: one glance at this one character pair already sketches a person.
The day master: Yi Yin Wood (乙)
Yi is the vine and the flowering stem: softer in form, tougher in survival. This day master adapts to whatever structure surrounds it, wins by flexibility and timing rather than force, and holds on where harder characters snap.
The day branch: si Snake (巳, 火)
Si is the Snake: metal rolling inside fire. As a day branch it adds strategy, patience in coiling, and sudden decisive strikes.
The si branch hides Bing Fire, Geng Metal, Wu Earth in its depths, which the full chart reads as secondary characters underneath the surface.
How the stem and branch interact
The stem pours its energy into the branch in the generating cycle: generous and expressive outward, but it pays for that expression from its own reserve.
What it is like when Yi Yin Wood sits on si
Here the producing cycle runs outward: the day stem pours its energy into the branch it sits on, like a lamp feeding its own flame. The classical image is generosity with a meter attached — the character expresses itself freely into the world, projects, and the people nearby, and pays for that expression from its own reserve. Traditional commentary reads this pairing as productive but expenditure-prone: the person gives more than they keep. The remedy the classics suggest is not restraint but replenishment — deliberate recovery, and an eye on what (and who) the outflow is actually feeding.
Taken together, the 乙巳 day pillar sketches a Yi Yin Wood day master whosesi ground absorbs it. Classical commentary always adds the same caveat: a day pillar is one character pair in a four-pillar chart, and the month branch — the season your chart was born into — can strengthen or exhaust any stem. Treat everything on this page as the first paragraph of the reading, never the whole of it.
The nayin of 乙巳: Lamp Fire
In the classical sexagenary verse system (nayin), the 乙巳 pillar is Lamp Fire (覆灯火). The nayin system assigns one of thirty poetic images to the sixty pillars two at a time: 乙巳 shares its image with 乙未, its neighbour in the cycle. The image belongs to a different element than the stem itself — nayin is a second, older layer of description laid over the pair.
Traditional commentators used the nayin image to summarise a pillar's texture rather than to compute with it. Lamp Fire is read as exactly that — an image of how the Yi Yin Wood / si combination feels from the outside. Treat it as flavour, not as a separate engine.
乙巳 elsewhere in the chart
The 乙巳 pairing does not only appear as a day pillar. The same stem-branch pair can occupy the year, month or hour pillar, and classical reading shifts its role with the seat: in the year pillar it describes the background — family atmosphere, early environment, the generational weather; in the month pillar, the season that sets the whole chart's balance, alongside the world of siblings, peers and career structure; in the hour pillar, the late chapters, children and private ambitions. When the same pair shows up in two seats, commentators read a doubling of its character — the themes above get a larger stage. If 乙巳 appears in your chart at all, it is worth knowing this page even if it is not your day pillar.
Find your own day pillar
Your day pillar comes from your birth date (the day changes at midnight, and in classical practice the hour matters for the other three pillars). The free BaZi calculator on this site computes your four pillars, hidden stems and ten gods locally in your browser, no sign-up needed. If your result shows 乙巳 on the day pillar, this page is you.
Frequently asked questions about the 乙巳 day pillar
It means your day master is Yi Yin Wood (乙) and it sits on the si(Snake) branch. The stem describes your core character; the branch describes the ground under it. Their combination (the stem drains into the branch) is the first sketch of how you carry that character.
It is the anchor, not the whole picture. Practitioners weight the day stem most heavily because every other element is judged from its position, but the month branch (your season) and the luck pillars tell you when that character gets its chances. Read all four pillars together.
Check the heavenly stem of your birth day. A free chart calculationtakes seconds; if the day pillar reads 乙巳, the description on this page applies to you. Your stem repeats every ten days, but the 乙巳 pairing comes around once in the full sixty-day cycle.
Two answers, both classical. By the stem: the day master is Yi Yin Wood, a Wood day master, and that is the element practitioners count first. By the branch: the si below it is Fire. In the nayin verse system the pair as a whole counts as Lamp Fire (覆灯火).
Once every sixty days. Days run in an unbroken sexagenary cycle — ten stems cycling against twelve branches, same-polarity pairs only — so each of the 60 pairings, 乙巳 included, falls on one day per full cycle. That fixed rhythm is why a birth date alone pins the day pillar down exactly.
Lamp Fire (覆灯火). The nayin system assigns thirty images to the sixty pillars two at a time, so 乙巳 shares the image with 乙未, the neighbouring pillar in the cycle. It is read as a poetic summary of the pair's texture, not as a separate calculation.