True Solar Time Offsets for 30 Major Cities: The BaZi Conversion Table
Last updated 2026-07-12 · 7 min read
TL;DR
BaZi hours follow the sun, not the clock. To convert your birth time, adjust by 4 minutes per degree of longitude between your city and its time zone's reference meridian — then subtract another full hour if daylight saving was in effect.
The table below gives the exact adjustment for 30 major cities, computed with the same engine BaziGPT uses for every chart. In Madrid the clock runs 75 minutes ahead of the sun; in Kuala Lumpur, 73; in Singapore, 65. If your adjusted time crosses a two-hour boundary, your hour pillar changes.
How to read this table
Each row shows how far a city's clock deviates from its true solar time, based purely on geography: the distance between the city's longitude and the reference meridian its time zone is anchored to. The rule is 4 minutes per degree — cities east of their meridian see the sun early (add minutes), cities west see it late (subtract).
Apply the adjustment to your birth certificate time. Example: born 15:10 in Hong Kong → 15:10 − 23 min = 14:47 true solar time. Still within the 未 Wei hour (13:00–15:00)? No — 14:47 is Wei, while 15:10 had already crossed into 申 Shen. One adjustment, different hour pillar, different chart.
The DST column matters just as much: if daylight saving was in effect on your birth date, subtract another 60 minutes before applying the longitude adjustment. That's where most Western charts silently go wrong.
The conversion table (computed, not estimated)
Adjustments below are calculated from each city's longitude against its IANA time-zone meridian — the same calculation BaziGPT runs automatically on every chart. Values are rounded to the nearest minute.
Why extreme cases are so common
Time zones are political, not astronomical. Spain runs on Central European Time for historical reasons despite sitting at Greenwich longitude — so Madrid's clock is a permanent 75 minutes ahead of its sun, before DST adds another hour on top. Singapore and Malaysia moved their clocks to UTC+8 in 1982 for business alignment with Hong Kong; the sun never followed.
China is the largest single case: one clock (Beijing time, 120°E) for a country spanning five natural zones. Chengdu's sun runs 64 minutes behind the clock; in Ürümqi it exceeds two hours — enough to shift the hour pillar twice.
The uncomfortable conclusion: for a large share of the world's population, the birth time on the certificate is not the time the sun would report. Any BaZi tool that skips this conversion is reading a chart for someone born somewhere else.
What this means for you
- You were born in Madrid, Kuala Lumpur, Singapore or Chengdu (offset > 60 min) — Treat any chart cast from raw clock time as suspect — your hour pillar has roughly a 50% chance of being wrong, and possibly the day pillar if you were born near midnight.
- You were born during summer in the US, Canada, Europe, Australia or New Zealand — Daylight saving adds a full −60 minutes on top of the longitude adjustment. Check both, in that order: subtract DST first, then apply the table.
- Your adjusted time lands within ~10 minutes of an odd-numbered hour (the two-hour boundary) — Your hour pillar is genuinely ambiguous. Cast both versions and see which chart's past reads true — the one that matches your life is the one that's yours.
- You were born in Taipei, Osaka, Manila or another near-meridian city (offset < 10 min) — You're in the safe zone: clock time and solar time are close enough that the conversion almost never changes your chart. DST is still worth checking for historical periods (Taiwan used DST 1945–1979).
Clock → true solar time, 30 cities (add/subtract minutes; DST −60 min extra when in effect)
| City | Longitude | Time zone | Adjustment | Has DST? |
|---|---|---|---|---|
| New York | 73.94°W | America/New_York (75°W) | +4 min | Yes |
| Los Angeles | 118.24°W | America/Los_Angeles (120°W) | +7 min | Yes |
| Chicago | 87.63°W | America/Chicago (90°W) | +9 min | Yes |
| Houston | 95.37°W | America/Chicago (90°W) | −21 min | Yes |
| San Francisco | 122.42°W | America/Los_Angeles (120°W) | −10 min | Yes |
| Seattle | 122.33°W | America/Los_Angeles (120°W) | −9 min | Yes |
| Toronto | 79.38°W | America/Toronto (75°W) | −18 min | Yes |
| Vancouver | 123.12°W | America/Vancouver (120°W) | −12 min | Yes |
| London | 0.13°W | Europe/London (0°) | −1 min | Yes |
| Paris | 2.35°E | Europe/Paris (15°E) | −51 min | Yes |
| Berlin | 13.40°E | Europe/Berlin (15°E) | −6 min | Yes |
| Madrid | 3.70°W | Europe/Madrid (15°E) | −75 min | Yes |
| Sydney | 151.21°E | Australia/Sydney (150°E) | +5 min | Yes |
| Melbourne | 144.96°E | Australia/Melbourne (150°E) | −20 min | Yes |
| Auckland | 174.76°E | Pacific/Auckland (180°) | −21 min | Yes |
| Taipei | 121.56°E | Asia/Taipei (120°E) | +6 min | No* |
| Kaohsiung | 120.31°E | Asia/Taipei (120°E) | +1 min | No* |
| Hong Kong | 114.17°E | Asia/Hong_Kong (120°E) | −23 min | No* |
| Macau | 113.55°E | Asia/Macau (120°E) | −26 min | No* |
| Singapore | 103.85°E | Asia/Singapore (120°E) | −65 min | No |
| Kuala Lumpur | 101.69°E | Asia/Kuala_Lumpur (120°E) | −73 min | No |
| Bangkok | 100.50°E | Asia/Bangkok (105°E) | −18 min | No |
| Jakarta | 106.85°E | Asia/Jakarta (105°E) | +7 min | No |
| Manila | 120.98°E | Asia/Manila (120°E) | +4 min | No |
| Tokyo | 139.69°E | Asia/Tokyo (135°E) | +19 min | No |
| Osaka | 135.50°E | Asia/Tokyo (135°E) | +2 min | No |
| Seoul | 126.98°E | Asia/Seoul (135°E) | −32 min | No* |
| Beijing | 116.41°E | Asia/Shanghai (120°E) | −14 min | No* |
| Shanghai | 121.47°E | Asia/Shanghai (120°E) | +6 min | No* |
| Chengdu | 104.07°E | Asia/Shanghai (120°E) | −64 min | No* |
FAQ
How were these numbers calculated?
Longitude difference from the time zone's reference meridian × 4 minutes per degree, using IANA time-zone data — the same engine BaziGPT runs on every chart. They are computed values, not estimates.
What does the asterisk (No*) in the DST column mean?
No DST today, but DST existed historically: Taiwan 1945–1979, Hong Kong 1941–1979, Macau until 1979, South Korea 1948–1960 and 1987–88, mainland China 1986–1991. If you were born in those windows, check our DST history tables — you may need the extra −60 minutes.
My city isn't listed. How do I calculate mine?
Find your longitude and your time zone's reference meridian (UTC offset × 15°). Adjustment in minutes = (your longitude − meridian) × 4. Or simply cast a chart on BaziGPT — the conversion is applied automatically from your birthplace coordinates.
Does a 20-minute offset actually change anything?
Only if it moves your birth time across a two-hour boundary (odd hours: 1, 3, 5…). Born 15:05 in Hong Kong? Solar time 14:42 — your hour pillar flips from Shen to Wei. Born 12:30? Solar 12:07, still Wu hour, nothing changes. The offset matters exactly when you're near an edge.
Should I also apply the equation of time?
Traditional BaZi practice uses local mean solar time — longitude and DST corrections only. The equation of time (±16 minutes seasonally) is an astronomical refinement most classical schools do not apply, and BaziGPT follows the traditional convention.
See it in your own chart
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