# What to prepare before creating a birth chart

Check the calendar, birth time and location before you begin, and know which details can remain unknown.

Canonical: https://wenbu.app/en/learn/prepare-birth-details/
Updated: 2026-09-30
Authorship: Wenbu · AI-assisted editorial

## The short answer

Record the date, local clock time, birthplace time zone and information source separately. Wenbu accepts Gregorian dates for BaZi and Zi Wei, but the tools use different time conventions. Preserve uncertainty instead of filling a default time, and avoid applying solar-time correction twice.

- Confirm the calendar and any leap month. The current tools accept dates from 1901 through 2099.
- Use the birthplace’s time rules on the birth date, not your current location.
- BaZi can omit an unknown hour. Zi Wei needs a known time; an uncertain chart remains a candidate.

**Check the date, time, time zone and source**

The cards select the first four checks: calendar type, recorded time and its precision, historical time-zone rules, and the information source. The complete table below adds day-boundary, longitude and Zi Wei settings, with guidance for uncertain inputs.

## Check which calendar the date uses

Wenbu’s BaZi and Zi Wei tools accept Gregorian dates. A birthday remembered as the fifth day of the fifth lunar month is not necessarily May 5. Confirm the year, calendar and whether a leap lunar month is involved before converting it with a reliable calendar reference.

A zodiac animal or an approximate age is not enough to produce a personal chart. You can use the example details to learn the interface, but keep that demonstration separate from your own birth record.

## Bring the details your chosen tool needs

BaZi and Zi Wei have different input requirements. Choose the tool first, then prepare the relevant details.

- BaZi: Gregorian date and the time zone at the birthplace. Add the birth time if known; otherwise use the unknown-time option.
- Optional BaZi settings: the day boundary, and approximate solar-time correction. Solar correction requires a longitude and a known time.
- Zi Wei: Gregorian date, known local birth time and the male/female parameter required by the current traditional algorithm. This setting does not define your gender identity.
- I Ching and tarot: no birth date, name or sex parameter is needed. Begin with the question you have now.

## A birth-information checklist

| Item | What to check | If uncertain |
| --- | --- | --- |
| Date | Year, calendar type and any lunar leap month. | Check the original record and convert to Gregorian before entering. |
| Time | An exact recorded time or an approximate range? | Select unknown time for BaZi rather than inventing minutes. |
| Time zone | The birthplace’s rules on the date, including historical daylight saving. | Confirm the city; ambiguous clock times need a verified offset. |
| Source | Certificate, hospital record, family note or recollection. | Keep the source and uncertainty in your notes. |
| Day boundary | Midnight or the start of Zi hour for BaZi. | Retain the default initially and record it for comparisons. |
| Longitude | Needed only for optional BaZi solar-time correction with a known time. | Leave correction off if the location is uncertain. |
| Zi Wei parameters | Known local time and the algorithm’s traditional sex parameter. | Study a sample first; the parameter does not define gender identity. |

## Use the clock time recorded at the birthplace

Suppose your birth record says 08:30 in Shanghai and you now live in London. For BaZi, enter that recorded local time with Asia/Shanghai, rather than your device’s current time zone. Historical daylight-saving rules depend on the birth date.

The Zi Wei tool uses the local date and clock time you enter. It does not inherit the BaZi time-zone or solar-time settings. Check each result’s calculation notes before comparing charts across tools.

## Record uncertainty instead of filling the gap

“My family remembers early morning” and “the birth certificate says 06:20” provide different levels of detail. Look for a certificate, hospital record or original note. BaZi can omit an unknown hour, with a warning that solar-term boundary dates may still leave a year or month pillar uncertain. Zi Wei currently needs a known time.

Near 23:00, midnight, an hour boundary or a solar term, keep the possible inputs and the differences between them. Do not select a chart solely because its interpretation feels familiar. Start by confirming the date and time zone; you do not need every advanced setting for a first visit.

## Worked example: two possible times around seven in the morning

Fictional practice data: October 20, 2010, Shanghai. A family note says 06:50; a recollection suggests 07:10. Neither has yet been confirmed.

1. Record both sources. Do not treat the midpoint, 07:00, as an observed time or choose whichever interpretation feels better.

2. For BaZi, select Asia/Shanghai and begin with unknown time. Read the warnings: an omitted hour does not remove all uncertainty near a solar-term boundary.

3. To study differences, calculate 06:50 and 07:10 separately with identical remaining settings. Label them candidate A and candidate B, then compare the fields actually returned.

4. Do not present either as a confirmed personal Zi Wei chart. Look for the original birth record. Agreement between interpretations cannot establish a missing clock time.

5. When better evidence arrives, note its source and calculate again. Preserve the earlier candidates and the conventions with your correction.

Preparation should produce traceable inputs with honest uncertainty, rather than a complete form filled with unsupported precision.

## Key terms

**Civil time** — The local clock date and time, including any applicable daylight saving.

**Time-zone identifier** — A name such as Asia/Shanghai representing time rules that can change historically.

**Candidate input** — One possible, explicitly unconfirmed set of birth details.

## Common questions

### Can I enter a lunar birthday directly?

No. Confirm the lunar year, month, day and leap-month status, then convert. The Hong Kong Observatory offers calendar tables for its stated coverage.

### Should I use my phone’s current time zone?

No. BaZi needs the birthplace’s historical rules. Zi Wei currently uses the entered local clock without importing BaZi’s time-zone or solar-time settings.

### Does solar-time correction guarantee a more accurate reading?

No. For a fixed birth instant it adjusts the BaZi day/hour clock; year/month retain absolute solar-term boundaries. This convention does not validate an interpretation.

## Sources and their scope

- [Wenbu · BaZi date and time conventions](https://github.com/Digidai/wenbu/blob/main/src/lib/bazi.ts) — Supports date limits, unknown-time handling, time-zone validation and correction scope; not predictive accuracy.
- [Wenbu · Zi Wei input conventions](https://github.com/Digidai/wenbu/blob/main/src/lib/ziwei.ts) — Supports local clock input, the traditional sex parameter and the absence of BaZi corrections.
- [Hong Kong Observatory · Gregorian-Lunar Calendar Conversion Table](https://www.hko.gov.hk/en/gts/time/conversion.htm) — Provides calendar conversion tables for 1901–2100, not validation of readings. Wenbu has its own narrower input range.
- [IANA · Time Zone Database](https://www.iana.org/time-zones) — Explains historical local-time, UTC-offset and daylight-saving rules. A current offset is not assumed to apply to every birth date.