How it works

Your chart is calculated. The reading is written.

Two quite different things happen here, and it is worth knowing which is which. The chart itself comes from deterministic arithmetic — the same birth details always produce the same four pillars. The written reading comes from a language model. It never touches the calculation.

What a chart actually is

A Chinese birth chart — the Four Pillars, or BaZi — is eight Chinese characters arranged in four pairs. Each pair is one pillar, and each pillar has a heavenly stem on top and an earthly branch below.

The four pairs are labelled by what they describe: the year you were born, the month, the day, and the two-hour period of the day. The stem of the day pillar — called the day master — is the symbol the whole system is read around. It is the one cell highlighted in the diagram below.

How the four pillars are derived

There is nothing statistical or generative about this part. It is calendar arithmetic, and it runs in the same direction every time.

Why the sun, not the clock

Time zones are a recent human invention; the sun is not. Two cities in the same zone can differ by an hour of actual daylight, and the traditional system was built around the sun, not the zone.

So before the pillars are derived, your clock time is adjusted toward local solar time. Two corrections are involved. The first covers how far your birth city sits from the centre of its time zone. The second — the equation of time — corrects for the fact that the Earth’s orbit is not a perfect circle.

In practice this matters less often than you might fear, and more sharply when it does. The correction is usually under an hour, so most charts are unaffected. But the hour pillar changes every two hours on the clock. If your birth time sits near one of those boundaries, a few minutes of correction is the difference between one hour pillar and the next.

Where our chart may differ from another tool’s

This is worth being blunt about: charting tools do not all agree. Two tools given the same birth details can return different day pillars. That is not a bug in either — it is a set of conventions that were never standardised.

The three that cause most disagreements are:

• Where the day ends. Traditionally the day turns at 23:00, the start of the two-hour period that spans midnight. Some schools instead turn it at midnight. We turn it at midnight, which is the more common convention in modern software.
• Whether to apply the solar-time correction at all. Some tools use the clock time as entered. We apply the correction by default.
• Which time-zone history is used. Historical offsets have changed more than once — China observed daylight saving from 1986 to 1991, for instance. We use the IANA time-zone database rather than hard-coded rules.

What the AI does — and does not

The model receives the finished chart as a short structured description: four pillars, the day master, how the five elements are distributed. It receives nothing else — not your birth date, not your city, not your coordinates.

Its only job is to turn that description into readable English. It is explicitly instructed to describe patterns the tradition associates with a chart, and explicitly forbidden from stating what will happen to you. It cannot change a pillar, and if it did, the chart shown alongside it would not move.

What we deliberately do not do

• We do not predict events, dates, or outcomes.
• We do not give medical, legal, or financial advice.
• We do not connect you with a human reader — there is no human in the loop.
• We do not sell or share birth details. There is no account, and you can erase what we remember at any time.

What is left is narrower than it sounds. We would rather say it plainly: a chart, computed the same way every time, with a written reading meant to be read slowly and argued with.