Method
How your birth details become a chart.
A few minutes can change a pillar near a time boundary. Here are the inputs, corrections, and conventions Truenoon uses, with a worked example you can compare with your own calculation.
Example inputs: August 15, 1992 at 09:12, London.
1 · The place becomes coordinates
You select a city from a local place index. Its coordinates identify the timezone, and historical clock rules resolve the offset for the birth date. The coordinates represent the selected place, not a hospital or street address, so check that the city is the intended one.
2 · The clock is corrected to the sun
For a valid local time, the engine adds a longitude correction and an approximate equation-of-time correction for that date. It rounds their total to the nearest minute. The result is the solar time used by this calculator; the method does not improve the precision of an uncertain birth record.
3 · The calendar assigns four pillars
The engine passes the corrected date and time to the lunar-typescript calendar library. Year and month pillars follow solar-term boundaries. The day follows the sixty-pair cycle, and the hour falls within one of twelve two-hour periods. Truenoon applies the late-Zi day convention described below.
4 · The engine calculates the phase sequence
The traditional Da Yun rule uses the year stem's polarity and the selected sex to set forward or reverse order. The interval to the relevant solar-term boundary determines the starting age. This produces a sequence of periods; any description of what a period means for your life is a separate interpretation.
- Recorded clock time
- 09:12
- Timezone that day
- Europe/London · UTC+1
- Longitude correction
- -61 min
- Equation of time
- -4 min
- Total correction
- -64 min
- Time used for the chart
- 1992-08-15 · 08:08
Calculated by the same engine used for personal charts. Displayed corrections are rounded; the total is rounded once when the chart time is set.
The conventions behind a reproducible chart
A chart is reproducible only when its boundary choices are stated. These are Truenoon's current BaZi calculation conventions; another calculator can reasonably return a different result when it makes different choices. Zi Wei has its own conventions, described below.
- Solar-term boundaries
- Year and month pillars use solar-term instants, rather than January 1 or Lunar New Year as their boundary.
- Calculation time
- When a birth place is resolved and its local clock time is valid, the engine applies the longitude and equation-of-time correction before assigning the pillars.
- Late-Zi rollover
- Truenoon uses the late-Zi convention: from 23:00 through 23:59 of calculation time, the day pillar advances to the following day.
- Historical clocks
- For the underlying BaZi chart, a repeated daylight-saving clock time resolves to the earlier occurrence. If the clock skipped the entered time, the entered time is retained without solar-time correction. Both the life-rhythm curve and Zi Wei map are withheld in either case until the birth time can be checked.
How the visual readings are calculated
How is the Zi Wei map calculated?
The current adapter uses iztro@2.6.1 with the default algorithm and records the convention version truenoon-ziwei-v1. It calculates twelve palaces, major and supporting stars, life and body palaces, birth-year transformations and decadal age ranges from the corrected birth details.
Only stars calculated in a palace are shown there. If it has no major star, that absence is preserved rather than filling it with an opposite palace's star. Short star descriptions explain traditional imagery; they are not measured personality traits.
Which Zi Wei calendar conventions does Truenoon use?
The Zi Wei birth year changes at Lunar New Year, unlike BaZi's solar-term year boundary. In a leap lunar month, days 1–15 use that month's number and day 16 onward uses the next month's number. At 23:00–23:59 of corrected time, Truenoon advances the Gregorian date once and calculates the next day's early Zi hour.
The adapter accepts corrected dates from 1900-01-01 to 2100-12-31; the normalized engine date must also remain within that range. Zi Wei decadal ranges use nominal ages from its own calculation. They are not the same as BaZi's cycle-start date or completed birthdays.
What does the life-rhythm curve measure?
Each point represents one calculated BaZi Da Yun period, with its actual stem-branch pair and calendar-year range. The start date and forward or reverse sequence come from the chart calculation. The childhood interval before the first Da Yun is excluded. The curve is not an annual forecast.
Cycle timing and pillars come from the Bazi calculation. Truenoon maps the stem and branch’s primary-element relationships to a relative inward-to-outward tendency using the same visual weights at every stage. This is not a fortune, wealth or success probability. Model: truenoon-rhythm-v1. Formula: score = 50 + 50 × (0.4 × stemProjection + 0.6 × branchProjection); the displayed result is rounded to an integer. Relationship projections are Resource -1, Peer 0, Output 1, Wealth 0.6 and Authority 0.2. The branch uses its primary element, not a sum of all hidden stems.
Ages follow the engine’s nominal convention: calendar year minus birth year plus one, not completed birthdays. The exact cycle-start date is listed separately.
What if the birth time is unknown?
Truenoon uses noon as a calculation assumption, omits the hour pillar, and marks the chart and report as reduced precision. The remaining pillars are calculated from that assumption. Near a day or solar-term boundary, the unknown birth time may also affect the day, month, or year pillar. The life-rhythm curve and Zi Wei map are not shown from an assumed birth time.
How to judge the written reading
The report uses the calculated chart as its starting material and may use AI-assisted writing. Checks cover selected chart facts and content rules; they do not guarantee that every description is correct or relevant to you. Traditional interpretations are not established by the calendar arithmetic. Compare them with your experience, and use the report's feedback option when a passage does not fit.