BaZi Four Pillars
How the four BaZi pillars are calculated
Four Pillars charting converts birth time into stem-branch structure through solar terms, day stem and hour rules. Understanding the boundaries helps you read the chart more carefully.
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Generate Full BaZi ChartFour Pillars Core Rules Reference
| Pillar | Boundary Rule | Common Error | Authority / Source |
|---|---|---|---|
| Year | Changes at Li Chun, not Jan 1 or Lunar New Year | Mistakenly changing year before Li Chun | Solar longitude 315° |
| Month | Changes at 24 solar terms | Using lunar 1st instead of solar terms | Standard solar transition data |
| Day | 60 Jiazi cycle, day changes at 23:00 | Ignoring late Zi hour day transition | Traditional early/late Zi separation |
| Hour | Wu Shu Dun method based on day stem | Ignoring DST and True Solar Time | Equation of Time correction |
Start with the year pillar
The year pillar usually changes at Li Chun, not simply on January 1 or Lunar New Year. Births before Li Chun may still belong to the previous pillar year.
Then check the month pillar
The month pillar follows the 24 solar terms. If the birth time is close to a term boundary, confirm the exact transition time.
Verify the day pillar
The day pillar is best checked with a reliable calendar or charting tool, especially for late zi-hour births around 23:00.
Finish with the hour pillar
The hour pillar depends on both birth hour and day stem. Daylight saving time, birthplace and true solar time may shift the boundary.
Where four-pillar calculation often goes wrong
- Whether the birth date is close to Li Chun or another solar-term boundary.
- Whether the birth time is around zi hour, especially after 23:00.
- Whether the birth year falls in a daylight-saving period.
- Whether birthplace and true solar time correction are needed.
FAQ
Does the year pillar change at Lunar New Year or Li Chun?
BaZi charting usually changes the year pillar at Li Chun. A birth after Lunar New Year but before Li Chun may still use the previous pillar year.
Why does the month pillar follow solar terms?
BaZi months follow solar-term boundaries, not ordinary lunar months. Yin month begins at Li Chun, mao month begins at Jing Zhe, and so on.
Is the hour pillar based only on clock time?
No. It depends on the birth hour and day stem, and boundaries may be affected by birthplace, daylight saving time and true solar time.
What if the birth hour is uncertain?
Start with the most likely hour and read hour-pillar conclusions cautiously. For a detailed reading, verify the birth record when possible.