Why BaZi charts differ: daylight saving, historical time zones and apparent solar time
Different charts: what should I check first?
Compare the same recorded date, time and birthplace first. Then check historical clock rules, the chosen solar-time method and the day-boundary rule. A longitude adjustment alone is not apparent solar time.
Keep any charts that remain plausible. A date conversion can be checked separately from whether an interpretation describes your life.
Before asking how a chart is interpreted, check how it was calculated. Historical clock conversion errors and differences between charting schools are separate questions.
Time at birth
| Place | What to check |
|---|---|
| Singapore / Peninsular Malaysia | Historical offsets included UTC+7:30 before 1982; occupation and earlier periods require date-specific checks. |
| Mainland China | Daylight saving applied during parts of 1986–1991; earlier regional records need separate checks. |
| Hong Kong, Macau and Taiwan | Some historical years used daylight saving. Do not assume continuous use across every summer. |
Historical time zones and daylight saving, 1900–2000
Singapore used UTC+7:30 from September 1941 to February 1942 and from September 1945 to the end of 1981; UTC+9 applied during the intervening occupation period. Check exact transition dates and earlier records separately.
Example: a Beijing record at 09:20 on 1 July 1988 uses the daylight-saving clock. Historical standard time is 08:20; the hour pillar changes from Yi-Si to Jia-Chen. This illustrates conversion, not a personal reading.
Longitude correction is not yet apparent solar time
One degree of longitude corresponds to roughly four minutes. These rounded differences compare local mean solar time with a UTC+8 clock, before the date-specific equation of time.
| City | Mean solar time vs UTC+8 |
|---|---|
| Urumqi | about 130 minutes behind |
| Kuala Lumpur | about 73 minutes behind |
| Singapore | about 65 minutes behind (using today’s UTC+8) |
| Chengdu | about 64 minutes behind |
| Guangzhou | about 27 minutes behind |
| Hong Kong | about 23 minutes behind |
| Beijing | about 14 minutes behind |
| Shanghai / Taipei | about 6 minutes ahead |
Apply the equation of time to obtain apparent solar time. Whether to use that time is a method choice; the tool retains a comparison with standard time.
Example: at 07:10 on 10 June 1975 in central Singapore (UTC+7:30), this tool calculates apparent solar time at about 06:36. The hour pillar changes from Jia-Chen to Gui-Mao. These are alternative time methods, not proof that one is uniquely correct.
Month pillars change at jie boundaries
The Yin month begins at Li Chun and the Mao month at Jing Zhe, not on a civil or lunar month’s first day. Not all 24 solar terms change the month pillar. Check the precise instant near a boundary.
State the late-Zi rule
Some schools change the day at 23:00, others at midnight. This tool keeps the current day pillar at 23:00–24:00 and derives the Zi-hour stem from the following day. Compare the rules before comparing readings.
Four checks
- Find the original record and its uncertainty.
- Check historical clock rules and whether daylight saving was already handled.
- Compare the chosen time method using the place and date.
- Keep alternatives near hour, day and solar-term boundaries.
Displayed calculation times use whole minutes and a simplified equation of time. Second-precise time-zone transitions do not establish second-level chart verification. The start of the 1900 range has limitations; request a manual check near boundaries.
For a manual check, email the birth date, time, city and source of the time. No name or identity-document image is needed. The web calculation stays on your device; if you choose to email details, email providers process that message.