Most modern clocks show civil time: a shared time zone used by a region. True solar time is a local astronomical measure based on the sun’s position relative to a particular longitude. The two are related, but they are not identical.
Why it appears in traditional chart tools
Some Zi Wei Dou Shu schools adjust a recorded birth time toward local solar time. The adjustment can be minutes or, near a time boundary, enough to change the traditional hour. Other schools use civil time or set different boundary rules.
What affects the calculation
- The city’s longitude, not just its country.
- The legal time zone in effect on the date.
- Daylight-saving rules in the location’s history.
- The current Zi Wei calculation convention’s boundary rule.
How AstroEW handles it
Our first version treats the Gregorian birth date and local civil time as the primary input. The result page shows the location, time zone, and whether an adjustment was applied. We do not hide a correction behind a mysterious “accurate” label.
When a result changes near a boundary, compare both interpretations and read the method note.
This is a calculation choice, not a claim that one school has exclusive authority. You can learn more in our method notes →
Trace the ideas
These public references support the historical or technical context on this page. Interpretive language is AstroEW’s educational framing, and different traditions and calculation conventions may read the same symbol differently.
- NOAA Solar Calculator · Background on solar position and equation-of-time concepts.
- timeanddate time-zone database · Historical civil time and daylight-saving context.
- AstroEW method notes · How location and time corrections are shown in a result.