What birth time changes
The calendar date supplies much of the natal foundation but does not complete a Zi Wei chart. Lunar month and hour Branch determine the Life and Body Palaces; the hour also places several supporting stars. A different Branch can move key reference points and change their connections.
Five minutes do not always create another chart. When both times remain inside one two-hour interval, the hour Branch normally stays the same. Risk concentrates near a boundary, where a place correction or recording error may move the moment into the adjacent interval.
Twelve Chinese hours are Branch intervals
The day is divided into twelve periods linked to the Earthly Branches. Most span about two civil hours: Chou roughly covers 01:00–03:00, Yin 03:00–05:00, and so on. Zi crosses midnight and requires careful treatment of the calendar date.
You enter normal hours and minutes; the calculator converts them to an hour Branch. “Around seven” is therefore ambiguous because it may fall at the end of Mao or the beginning of Chen.
Why place, longitude and time zone matter
A recorded birth time is civil local time, governed by a time zone and the historical rules of that date. Solar noon also varies with longitude, so two cities in one time zone can differ relative to the Sun.
Green Jade can use the chosen place to supply coordinates and a time zone and calculate a true-solar-time adjustment. If no place is selected, the interface clearly uses its default. Choose the actual birthplace when the time is near a Branch boundary, and do not substitute today's time-zone rule for a historical one.
How to handle a boundary time
Preserve the source
Separate a document's exact entry from a family memory such as “early morning.”
Verify place and zone
Check the birthplace and the UTC offset used on that historical date.
Review the adjustment
If calculated solar time crosses a Branch boundary, keep both plausible versions.
Compare whole charts
Compare all Twelve Palaces, Ming, Shen and stars instead of choosing one pleasant description.
Different calculators may use different rules for the time zone, solar adjustment, late Zi hour, lunar conversion or school. Compare settings before declaring one result wrong.
When birth time is unknown
Start with records: a certificate, archive extract, medical record or family notes. Ask whether the time was copied exactly or rounded. If no source survives, build several scenarios and mark what stays stable and what moves.
Do not combine convenient pieces of different charts. Rectification from life events depends on a school and an interpreter; it does not turn an inference into a documented time. With material uncertainty, use the chart as an educational scenario or compare systems by question.
Checklist before calculation
- date checked against a source;
- time recorded with minutes and confidence level;
- actual birthplace selected;
- historical time zone considered;
- distance from an hour boundary reviewed;
- uncertainty kept visible;
- no chart symbol treated as a guaranteed event.
Then open the Zi Wei calculator, locate 命 and 身, and continue with the Twelve Palaces.
Frequently asked questions
Can Zi Wei be built without a birth time?
Not reliably. An assumed hour creates an assumed chart and must not be presented as precise.
Is accuracy to one hour enough?
Often, when the time is far from a Branch boundary. Near a boundary, minutes, place and time zone matter.
Why do two calculators disagree?
Check time-zone history, solar correction, the Zi-hour date rule, lunar conversion and school settings.