Inner, outer and secret animals: the Four Pillars connection
Four animals, not one — and three of them come from information most people never enter.
4 min read · Published 21 August 2026
The short answer
Popular Western presentations of Chinese astrology often give four animals: the outer or year animal from your birth year, the inner animal from your birth month, the true or secret animal from your birth hour, and sometimes a fourth from the day. These map directly onto the four branches of a BaZi chart. The framing is a Western repackaging — traditional practice reads the four pillars rather than assigning them these labels — but the underlying data is real.
The four animals and where they come from
| Name | From | Said to describe | BaZi equivalent |
|---|---|---|---|
| Outer animal | Birth year | How others see you | Year branch |
| Inner animal | Birth month | Your inner drives and motivations | Month branch |
| True or secret animal | Birth hour | Who you are privately | Hour branch |
| Day animal | Birth day | Your closest relationships | Day branch |
The right-hand column is the point. These are the four earthly branches of a BaZi chart, with English labels attached. Nothing is being computed that a Four Pillars chart does not already contain.
The labels are a Western addition
Traditional Chinese practice does not use 'inner, outer and secret'. It reads four pillars, each with a stem and a branch, and assigns each pillar a domain — year for wider environment and ancestry, month for parents and formative years, day for self and partner, hour for children and later life.
The inner/outer/secret framing appears in Western popular astrology, where it packages the same information as a more evocative set of hidden selves. It is not a mistranslation and it is not fraudulent — it is a repackaging, and the data underneath is genuine.
Worth knowing mainly so you are not surprised when a Chinese practitioner does not recognise the terms.
Why the month animal is not what you would guess
A common error: assuming the month animal follows the calendar month. It does not.
The month branch is determined by solar terms, the twenty-four divisions of the solar year, not by calendar months or lunar months. Each month branch runs from one major solar term to the next, and those fall around the 4th to 8th of each Gregorian month rather than the 1st.
So someone born on 2 February has a different month branch from someone born on 10 February, even though both are 'February'. This is the same solar-term system that decides the BaZi year boundary, and it is why a chart computed from calendar months is wrong.
What this gets you
- Specificity. One animal is shared by roughly one person in twelve. Four animals together are shared by roughly one in twenty thousand.
- A reason to find your birth time. The hour animal needs it, and so does a complete BaZi chart.
- A route into the real system. If the four-animal framing is what makes Four Pillars interesting to you, that is a perfectly good entry point — the branches are genuine even if the labels are not traditional.
The step beyond
The four animals are the branches. What the popular framing leaves out is the stems sitting above them — the other four characters of the eight, including your Day Master, which is the character a practitioner actually reads first.
So the inner/outer/secret presentation gives you half the chart, arranged attractively. AsterNym computes all eight characters plus the stems hidden inside each branch, on your BaZi page.
Common questions
- What are inner, outer and secret Chinese zodiac animals?
- A Western framing in which the outer animal comes from your birth year, the inner from your birth month, and the secret or true animal from your birth hour. They correspond to the year, month and hour branches of a BaZi Four Pillars chart.
- Is the inner and secret animal system traditional?
- The labels are not. Traditional Chinese practice reads four pillars, each with a stem and branch, and assigns domains to each pillar rather than calling them inner, outer and secret. The underlying data is the same.
- How do I find my secret animal?
- It is the earthly branch of your birth hour, determined by which two-hour period you were born in — from the Rat at 23:00 to the Pig at 21:00. It requires knowing your birth time.
- Is my month animal based on the calendar month?
- No. The month branch is set by solar terms, which fall around the 4th to 8th of each Gregorian month rather than the 1st. Two people born in the same calendar month can have different month branches.