How Yuanzi Calculates a Bazi Chart

Direct answer

Yuanzi Zhiyi first uses the birth date, time, place, and selected time convention to establish the Four Pillars, then derives the Ten Gods, hidden stems, Na Yin, Twelve Stages, and luck cycles from the Day Stem. AI does not establish the pillars or luck-cycle timeline. The sources are separated into Traditional charting rules, Modern civil-time data, and Modern true-solar approximation; each supports a different part of the published method.

Calculation chain

Traditional charting rules

Inputs, calendars, and solar terms

Users may enter a Gregorian date, a Chinese lunar date, or the Four Pillars directly. Date mode validates the actual number of days in a month, while lunar mode retains the leap-month flag. The Month Pillar follows the Zi Ping solar-term convention.

The Month Pillar follows solar-term months rather than changing on lunar day one. Exact time matters near a solar-term transition. When users supply only the pillars, the application does not reverse-engineer a seemingly precise birth date or luck-cycle start time from insufficient evidence.

Modern civil-time data

Recorded civil time

The default is the civil clock time recorded at the birthplace. Modern civil-time data reconstructs the birth instant; it does not determine traditional charting rules.

Modern true-solar approximation

When a user selects true solar time and a known place, the page uses:

true solar time = recorded local civil time + longitude correction + equation of time

• The UTC offset on the birth date comes from IANA timezone history, including applicable daylight-saving rules. IANA is one major civil-time reference; pre-1970 or disputed records still require local official sources.
• The recorded wall time is first resolved to one birth instant and compared with solar terms on the same timeline. Skipped or repeated daylight-saving clock times are not silently guessed.
• Reference meridian derived from the UTC offset at that instant = UTC offset in minutes ÷ 4.
• Longitude correction = 4 × (birthplace longitude − reference meridian) minutes.
• The equation of time uses the approximation published on the tool page. The combined result is rounded to a whole minute before the Day and Hour Pillars are evaluated; results within one minute of a boundary should be checked against adjacent times.

The True Solar Time Bazi Calculator exposes each component and its limitations. PNNL-30028, Appendix A, directly documents the 364-day approximation used here. NOAA Solar Calculator equations documents the total solar-time offset relationship but uses a different equation-of-time approximation. Modern civil-time data primarily references the IANA Time Zone Database. This is designed for chart-boundary comparison, not high-precision ephemeris work or legal time certification.

3. Day and Hour Pillar boundaries

The Hour Pillar follows traditional two-hour branch periods. For 23:00–23:59, the application exposes two day-boundary conventions:

• 23:00 early-Zi boundary (default): the Day Pillar advances at 23:00.
• 00:00 midnight boundary: 23:00–23:59 remains on the current sexagenary day.

San Ming Tong Hui states that the Hour Stem follows the Day Stem. The Hour Stem is therefore recalculated from the Day Stem actually selected by the boundary: a Geng day gives Bing-Zi, while a Xin day gives Wu-Zi.

This is an explicit lineage choice, not a browser-timezone guess. The birthplace civil time and solar terms are first placed on one absolute timeline to determine the Year and Month Pillars. Local time correction and the selected day boundary then determine the Day and Hour Pillars. The page compares all four pillars and identifies any difference.

4. Ten Gods and derived chart structure

The Ten Gods are determined from the generating/controlling relationship and polarity of the Day Stem and each target stem. Hidden stems use a fixed branch table and are then evaluated relative to the Day Master. Na Yin, Twelve Stages, void branches, and deterministic combinations or clashes follow the declared traditional relationships rather than being filled in by a language model.

These are structured terms within a traditional interpretive system. They are not modern scientific proof of personality, health, wealth, or future events.

5. Luck cycles and starting age

The starting convention follows San Ming Tong Hui, “On Major Luck Cycles”: the traditional sex option and Year-Stem polarity determine direction; forward charts count to the following adjacent jie, reverse charts to the preceding adjacent jie, and three days are converted to one year with remaining months, days, and hours retained. The first start is displayed in the birthplace civil time in effect at that later date.

A direct-pillar input or an unknown birth hour lacks the information required for a reliable precise start. The application marks the timeline unavailable instead of inventing an age.

6. Incomplete time or place

• Unknown hour: the Hour Pillar remains unknown; true-solar correction and hour-dependent precision are withheld.
• Unknown minute: the page uses the whole hour as an approximate input and labels it clearly. If correction could cross an hour, day, or solar-term boundary, compare adjacent results instead of treating the whole-hour result as an exact birth time.
• Unmatched birthplace: the recorded civil time is retained and true solar time stays unavailable; coordinates are not guessed from free text.

7. Where AI participates

AI may explain an already calculated chart and answer follow-up questions. It may not change the Four Pillars, birth record, calendar result, or luck-cycle table. Medical, legal, financial, and immediate-safety decisions still require qualified people and current evidence. Bazi is presented as a traditional cultural lens, not a deterministic forecast.

8. Conventions and verification record

Fixed cases let readers check whether the same declared convention continues to produce the same result. See Reproducible Bazi Calculation Cases for day-boundary, true-solar, fixed-chart, and unknown-time examples. When tools disagree, compare calendar input, timezone, true-solar setting, day boundary, and luck-cycle convention before calling one result “more accurate.”