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True Solar Time

Input parameters

Birth date (Gregorian)

Year

Month

Day

Birth time (clock time)

Hour

min

Birth place

Longitude (auto-filled or manual)

East longitudes are positive; west longitudes are negative

Calculation result

Enter the parameters, then click "Calculate true solar time"

What is true solar time?

True solar time is based on the Sun's actual position and is directly related to local longitude. China uses Beijing Time (120°E), but true solar time varies by region.

Longitude correction:Each degree east advances true solar time by 4 minutes; each degree west delays it by 4 minutes. For example, Chengdu (104°E) is about 64 minutes behind Beijing Time.

Equation of time correction:Because Earth's orbit is elliptical and its axis is tilted, the length of a solar day varies through the year. This is the equation of time, reaching about ±16 minutes.

Shichen determination:Traditional shichen uses true solar time, so chart calculation should use it instead of clock time to determine the birth shichen.

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