Why Zi Wei Dou Shu charts differ between websites
You entered the same birth data into two calculators and got two different charts. That's common, and usually neither tool is “wrong” — their conventions differ. These are the eight most frequent reasons, ordered by how easily they're overlooked, plus a checklist.
1. Year boundary: Lunar New Year or Li Chun
The birth-year stem determines the birth-year transformations, the palace stems and the Five Elements Bureau, so this changes the entire chart. Most Zi Wei Dou Shu tools change the year at Lunar New Year; some use Li Chun. It only matters for births between the two dates (late January to early February).
2. Whether true solar time is applied
Some sites use the clock time as is; others correct for the birthplace's longitude. A difference of tens of minutes can move the birth into the neighbouring double-hour and change the Life and Body Palaces.
3. Whether daylight saving is handled
Mainland China observed daylight saving in the summers of 1986–1991, Hong Kong until 1979 and Taiwan in 1974–75 and 1979. The clock ran an hour ahead of standard time; ignoring it puts many births in the wrong hour.
4. Which time zone is assumed
For births abroad, the clock time is local time: convert with the local time zone first, then apply true solar time — not always Beijing time.
5. Which day the late Zi hour belongs to
Whether 23:00–23:59 counts as the same day or the next differs by school and tool; it shifts the day by one and so the Zi Wei star position.
6. Leap-month assignment
The Quan Shu convention puts days 1–15 of a leap month in that month and the rest in the next; some tools put the whole leap month in one or the other.
7. Star-placement school
The standard and Zhongzhou methods place some stars differently.
8. Four-transformation table
Schools differ on a few stems, which changes the birth-year transformations.
Checklist
Compare the year boundary first; then the clock time and birthplace (true solar time, time zone, daylight saving); then the late Zi hour and leap months; finally school and transformation table. If the first three match, the Life Palace, Body Palace, Five Elements Bureau and Zi Wei position should agree exactly — 9zi.ai has verified those four against independent classical formulas (see the verification report).
Q: Two sites give different Life Palaces — which is right?
Check that the year boundary, true solar time and daylight saving conventions match first. The Life Palace depends on the birth month and the hour, so a different hour is the usual cause.
Q: What if I was born during daylight saving?
Enter the clock time as it was. The calculator removes daylight saving automatically using the birthplace's time zone.