It converts your local clock time to true solar time, casts the nine palaces by the Hour-based Rotating Plate (Chai-bu) method, and then explains what is on the chart in plain language.
Qimen Dunjia is the most structurally intricate of the Chinese divinatory arts: the moment is converted to stems and branches, the yin/yang cycle and the ju number are fixed, and then the nine stars, eight gates, eight spirits, and the heaven/earth stems are laid into nine palaces by rule. The whole derivation is deterministic — same moment, same longitude, same chart, for anyone.
This site uses the Hour-based · Rotating Plate · Chai-bu school, rolls the day at 23:00, and corrects clock time to true solar time by longitude (the clock face only — solar-term boundaries are untouched). Flying-plate, yin-plate, and intercalation rules from other schools are deliberately kept out: mixing schools is the single most common error here, and once mixed, charts can no longer be compared against each other.
There is no "close enough" in casting: it is either right or wrong. So it is pinned down in tests — the nine-palace diagrams from the books, one cell at a time. If a change to the engine puts a single cell out of place, the code does not ship.
Once the chart is cast, something still has to decide which palace answers your question. Get that wrong and every sentence afterwards is describing a different matter.
We publish that number: across 321 casebook examples, the palace it picks matches the author's 68.8% of the time. Roughly one time in three it is looking somewhere else. That is not a flattering number, but it is the real one, and we keep working on it.
The reading text is generated by an AI from the cast chart. It is for reflection only and is not medical, financial, legal, or psychological advice, nor a substitute for a doctor, a lawyer, or a financial adviser. For decisions that matter, come back to the real world and talk to a professional.
First time looking at one of these? The app has a one-minute page explaining the nine palaces, the five symbols in each cell, and which cell is "you".
Casting, the 3D nine palaces, per-palace imagery, pattern analysis, and multi-palace combinations — free forever, no account needed.
Only the AI reading is metered, because each one is a real call to a language model. Signing in gives you 1 free reading; after that:
Readings live on your account — switch devices or browsers and they are still there, and they do not expire. Payments are handled by Stripe; we never see your card number. Crisis responses, safety messages, and any attempt where the AI did not come through are never charged.
Location is used only to compute true solar time and to show your city name. Casting happens entirely on your device and works offline. Only when you tap Read do your question and a summary of the chart go to the reading service to write that one reply — not stored, not tied to your identity. Signing in uses your email solely to remember your reading balance: no ads, never shared. See the Privacy Policy.