Chinese astrology guide
BaZi Four Pillars, stems, branches, and Day Master
BaZi converts a birth moment into four stem-branch pairs representing year, month, day, and hour.
Chinese Astrology · 9 minute read
Written and reviewed by ReadAstrology Editorial & Calculation Team. Published 2026-07-18T00:00:00-05:00. Modified 2026-07-18T00:00:00-05:00.
Key takeaways
- BaZi requires four separate stem-branch calculations.
- The Day Master comes from the day pillar, not the zodiac animal.
- Calendar and time-boundary conventions must be explicit.
Methodology: The public preview states its civil-time and boundary assumptions and does not claim full traditional strength analysis.
Astrology and numerology are cultural and symbolic traditions, not scientifically validated methods for predicting events, diagnosing conditions, or guaranteeing outcomes.
Sources and calculation references
- Gregorian-Lunar Calendar Conversion Table — Hong Kong Observatory. Gregorian and traditional Chinese calendar boundary verification.
- The Chinese Agricultural Calendar — Hong Kong Observatory. Lunisolar calendar structure, lunar months, solar terms, and leap months.
- IANA Time Zone Database — Internet Assigned Numbers Authority. Historical civil-time offsets and daylight-saving rule provenance.
Eight characters from four pillars
Each pillar contains one Heavenly Stem and one Earthly Branch. Four pillars therefore produce eight characters, which is the origin of the name BaZi.
The result is deterministic only after the calendar, year boundary, month boundary, day rollover, timezone, and hour rules are fixed.
The Day Master
The Heavenly Stem of the day pillar is called the Day Master. Traditional analysis compares it with seasonal context, other stems and branches, hidden stems, and element relationships.
The Day Master is not calculated from the year animal and cannot be inferred from the birth year alone.
Month and hour boundaries
BaZi month pillars commonly follow solar terms rather than Gregorian months. The hour pillar changes in two-hour branch periods and may be affected by true solar time conventions.
A preview that uses civil time without true-solar correction should say so clearly.
Element balance is not a simple score
Counting visible wood, fire, earth, metal, and water characters is only a first screen. Traditional strength analysis includes season, roots, combinations, transformations, and hidden stems.
Software should avoid turning a simplified count into a deterministic claim about personality or fate.
Frequently asked questions
What are the Four Pillars in BaZi?
They are the year, month, day, and hour pillars, each containing a Heavenly Stem and Earthly Branch.
What is the Day Master?
It is the Heavenly Stem of the day pillar and a central reference point in traditional BaZi interpretation.
Does BaZi use Lunar New Year or Li Chun?
Many BaZi methods use solar-term boundaries such as Li Chun. The exact convention must be disclosed by the calculator.