How Jade Zodiac Calculates Your Chart

The Four Pillars (Ba Zi) tradition

A Ba Zi (八字, "Eight Characters") chart has four pillars — Year, Month, Day, and Hour — each written as one Heavenly Stem (天干) and one Earthly Branch (地支). Together those eight characters describe the elemental makeup of a birth moment.

Our interpretations follow the classical Four Pillars tradition documented in foundational texts such as San Ming Tong Hui (三命通會), the Ming-dynasty Ba Zi compendium. We treat it as a source in the tradition — the pillars themselves are computed with the solar-term calendar the classics rely on, brought to modern precision with the Swiss Ephemeris.

Li Chun, not Chinese New Year

For Four Pillars, the year pillar changes at Li Chun (立春) — the solar term "Start of Spring," around February 4 — not at lunar Chinese New Year. Many popular zodiac sites use the New Year boundary; that is fine for casual zodiac but incorrect for Ba Zi.

The difference is real and it matters for boundary births. In 2027, Li Chun falls about February 4 while Chinese New Year is February 6 — so someone born February 4–5, 2027 is already a Fire Goat by Ba Zi even though the lunar new year hasn't arrived. We always use the Ba Zi-correct Li Chun cutoff.

Astronomical precision

• Solar terms & Li Chun are derived from the Swiss Ephemeris, the same high-precision astronomical engine used in professional astrology software.
• The day pillar is computed with the Julian Day Number method, the standard for accurate calendar conversion.
• True solar time is adjusted for your longitude and the equation of time, so the Hour Pillar reflects the actual sky at your birthplace rather than clock time.

Do you need your birth time?

Birth time sets the Hour Pillar (a two-hour 時辰 period), so an exact time yields the complete four-pillar chart. If you don't know your birth time, the Year, Month, and Day pillars — three of the four — are still calculated accurately, and your zodiac animal, element, and Day Master are unaffected.

How our written reports are produced

The chart is calculated deterministically by the engine above. The written interpretation is then generated from that verified chart data and reviewed against an accuracy rubric before it reaches you — so the prose always describes your computed pillars, not a generic horoscope.