Sukuyo birth mansion table: month starts and counting
A Sukuyo birth mansion table starts from the converted lunar month’s assigned mansion and advances by lunar day minus one through 27 entries.
Overview
Day one stays on the month’s listed starting mansion. The worked example shows how later days advance and wrap around the roster.
At a glance
- Months 1–4
- 室・奎・胃・畢
- Months 5–8
- 参・鬼・張・角
- Months 9–12
- 氐・心・斗・虚
Read the right date
Use a converted lunar month and day, not a Gregorian month/day with the same numbers.
The conversion convention remains part of the result even when the lookup table is printed separately.
Count inclusively
Lunar day one is the listed starting mansion. Day two is one step forward, so the offset is day minus one.
After the last mansion, continue from the first without adding 牛 to the 27-entry product sequence.
Worked lookup example
For lunar month one, day one gives 室 and day two gives 壁. Day six wraps to 昴.
These are table examples, not claims that an unspecified Gregorian birthday converts to those lunar dates.
End-of-month handling
A 27-position cycle can wrap before a lunar month ends. Use the actual converted day rather than forcing a month to contain 27 days.
A lunar day 30 is valid only when the calendar conversion supplies it; the lookup must not create nonexistent dates.
Compare with the historical table
T1299 volume one begins its first-day row with 虛, while this modern product table begins with 室.
Keep the two tables labeled. Do not publish the product row as a verbatim transcription of the classical source.
Verify the arithmetic independently
Write the zero-based month-start index as s and lunar day as n, then check index = (s + n − 1) mod 27 against the printed roster. Test day one and one wraparound case.
This verifies the table step only; it does not verify that the preceding lunisolar conversion or the interpretation is correct.
Sources and editorial basis
- 宿曜經 · T1299 卷上卷上「大唐月建圖」first-day row begins 虛; deliberately not represented as OpenFate’s 室-start table.Historical text for mansion names and calendar tables. Its table is not identical to OpenFate’s modern 27-mansion lookup; it does not establish predictive validity.
- OpenFate Sukuyo calculator and calculation conventionEditorial code check 2026-09-10, policy 1.0.0: lookup-table; policy.ts, constants.ts, engine.ts and traditional-cycles.ts. Product settings are not an independent historical authority; practical examples are OpenFate editorial applications.Product-specific input and output reference. Editorial checks also inspected policy 1.0.0 and the month-start constants on 2026-09-10; those implementation checks are not an independent traditional authority.