Charting often uses true solar time, not the clock time on your phone. Correction does not always change your Chinese hour—but without understanding it, you will not know when to double-check. Below: what it is, then when a few minutes really flip the chart.
Three kinds of time
- Clock (standard) time—what is on your birth certificate
- Local mean solar time—adjusted for birthplace longitude vs the time zone's standard meridian
- True solar time—mean solar time plus the equation of time (Earth's elliptical orbit)
Chart-reading systems place you in a two-hour Chinese hour slot (or equivalent) from solar time—not from the wall clock alone.
Two corrections
- Longitude—Beijing (~116°E) vs China's 120°E meridian: about −14 minutes; Taipei (~121.5°E): about +6 minutes
- Equation of time—roughly ±16 minutes depending on date
Honest first: not every correction flips the chart
If you were born in the middle of an hour slot, a few minutes of correction usually keep the same hour. Example: Taipei 07:20 on 1994-03-21, after Zi Wei's longitude + equation-of-time correction (~07:18), stays in the 辰 hour (7–9 AM slot)—the whole chart does not remap from that alone.
When it does matter: Beijing 07:02
1994-03-21, 07:02 Beijing time:
- Clock 07:02 → Chen hour (7–9 AM)
- After longitude + equation of time ≈ 06:40 → Mao hour (5–7 AM)
The hour changed—Life Palace, BaZi hour pillar, or ascendant can all shift. That is when “a few minutes” is real.
Larger longitude gaps
- Chengdu 07:10 clock → ~05:58 solar (~−1h12m)
- Urumqi 10:00 clock → ~07:43 solar (~−2h10m)
The big demo gap in our comparison article is mostly AI inventing a chart—not Taipei's few minutes of solar-time correction flipping palaces. This post is only about when time correction changes the hour.
Worth careful correction
- Within ~15–20 minutes of an hour boundary
- Far from the time zone's standard meridian
- Cross-checking software or AI—need one time standard
- Client or professional work
Lower risk (still fill birthplace)
- Middle of the hour slot, only a few minutes correction
- Rough reading and you already match your practitioner's setup
Zi Wei—often longitude + equation of time.
BaZi—some tools use longitude only; confirm before comparing. Astralium BaZi labels longitude-only correction in the packet.
Western astrology—houses are time-sensitive; confirm house system too.
- Birthplace filled in
- True solar time on/off and equation of time included or not
- Corrected time or ± minutes shown in output
- Near boundary: try ±15 minutes
- Give AI the corrected time standard, not just “7 AM”