How it works
How your reading is generated
Purple Tome is two things working in sequence — and it matters which does what.
First, the engine.
Your chart is cast by a deterministic charting engine. Your birth data is converted to true solar time — resolving the daylight-saving rule in force at your birthplace on that specific date, then correcting for longitude, then for the equation of time — and resolved to the classical two-hour block. The twelve palaces, the stars, and the Four Transformations are then computed by fixed classical rules.
Same input, same chart, every time — down to the daily cycle. This part involves no AI at all. It is math, and it is tested: every heavenly stem's transformation set is verified against the classical tables, and the daylight-saving edge cases that decide your hour pillar are covered by their own tests.
Then, the translation.
The written reading is generated by AI — one we've purpose-built and constrained for a single job: translating what the computed chart says into plain English, following interpretation rules grounded in the Ming-dynasty classics. It never casts the chart, and it never invents a placement. If a star isn't in the computed chart, it cannot appear in your reading.
The AI never casts it; it only translates it.
Why you can't get this from a chatbot
Ask a general-purpose chatbot to cast your Zi Wei chart and it will produce something that looks right — with stars in the wrong palaces and transformations from the wrong year, and no way for you to check. The value of a computed chart is that it can be wrong or right — and ours is built, tested, and corrected in the open.
| A general chatbot | Purple Tome | |
|---|---|---|
| Casting the chart | Recalled on the spot. Stars land in the wrong palaces — and you have no way to check which ones. | Computed by fixed classical rules. Deterministic output, identical every time. |
| True solar time | No longitude correction, no historical daylight-saving rule. | Daylight-saving rule in force at your birthplace on that date, then longitude, then the equation of time. |
| Time resolution | No era / year / month / day structure. Invents a fresh answer each time you ask. | Era → year → month → day, each layer derived and inspectable. |
| Consistency | Ask twice, get two different charts. | Same chart, same structure, reproducible conclusions. |
| Accountability | An error can be neither found nor fixed. | Transformation tables under test; corrections published openly. |
Ours can be checked. That's the whole difference.
What we won't claim
There is no human astrologer reviewing your reading, and we won't pretend otherwise. We also won't claim the readings are never wrong — classical schools genuinely differ on some points, and we follow one school consistently. What we do claim is narrower and checkable: the chart is reproducible, it is tested, and when we get something wrong we fix it and say so.
Purple Tome is a tool for reflection — not a substitute for a human practitioner, and not medical, financial, or legal advice.