True solar time in Bazi: longitude correction and hour-pillar boundaries
Explains why true solar time matters for Bazi charts, especially near hour boundaries and day-change rules.
True solar time adjusts clock time to the Sun’s position at the birthplace and can change the Bazi hour pillar near boundaries.
Search Intent
Searchers want to know whether the same clock time gives a different chart in another city. The key variables are longitude, time zone, and boundary distance.
Evidence Block
Every 1 degree of longitude is about 4 minutes of solar-time difference. Births within about 15 minutes of an hour boundary need careful review.
Workflow
Record the civil clock time, then enter city or longitude. If correction crosses a Chinese double-hour boundary, compare both candidate charts.
Use Lingtai birth-time tools to check true solar time, hour changes, and day-boundary risk.
Short Answers
Is true solar time always required?
It matters most near hour or day boundaries.
How much does longitude matter?
One degree of longitude is about four minutes.
Is Zi hour sensitive?
Yes, because it can also involve day-change rules.