True solar time: check the time basis first

Convert a UTC+8 clock time using the 120°E standard meridian; inspect longitude, equation of time and date rollover.

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Input parameters

Clock basis: UTC+8 / standard meridian 120°E

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East longitudes are positive; west longitudes are negative

Calculation result

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

Six-system reading · see a doctor for persistent symptoms

Entering a birth time recorded outside China

  1. This input is interpreted as UTC+8. For an overseas local record, first check the legal time zone and daylight-saving offset on that date, then convert the same instant to a UTC+8 date and time.
  2. For example, January 1 at 10:00 with a verified UTC−5 offset becomes January 1 at 23:00 UTC+8. This example applies only when that record used UTC−5. Carry any day change into the date; longitude and time zone are different inputs.
  3. Then enter the actual birth longitude to calculate the longitude adjustment and equation of time. The BaZi handoff retains the original UTC+8 time and longitude so the engine corrects it once, not twice.
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Which clock time does this tool accept?

This tool always interprets input as UTC+8 with a 120°E standard meridian. East longitude is positive. Verify an overseas clock time, historical daylight saving or historical civil offset before converting it to UTC+8; entering an overseas city does not convert its time zone. City suggestions only help fill longitude.

How the corrections combine

The longitude term is (local longitude − 120°) × 4 minutes. Adding the equation of time gives approximate apparent solar time. Production rounds longitude to a whole minute, calculates the date-based equation of time to 0.1 minute, then displays whole minutes. Ledger amounts are also rounded. This is not a second-level ephemeris.

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A rollover changes the date too

For the synthetic input 2024-01-01 00:05 at 116.4°E, production returns 2023-12-31 23:47, the previous day. At 120°E, 2024-11-03 23:55 becomes 2024-11-04 00:11. When calculating a chart next, retain the original clock date and longitude and let that engine correct once; do not correct an already corrected time again.

Which fields keep the input date?

The lunar date and solar-term helper fields use the original clock calendar date, not the corrected date or an exact term comparison. BaZi year and month pillars use the original absolute instant for solar-term boundaries; day and hour pillars use solar time. Starting Zi hour at 23:00 and changing the day pillar are separate conventions.

Use the result carefully

Verify the source time zone and daylight saving, then check longitude, rollover and traditional hour. Keep the solar-time convention consistent across calculators. A minute-level display cannot make a birth record recorded only to the nearest half hour more reliable.

Continue your task

Open the BaZi calculatorInspect 24 public boundary inputs and calculation rules

Sources and further checks

US Naval Observatory: equation of timeNOAA: solar time and time-zone equations (independent approximation)

Maintained by the Fateverse project content team. This page explains the current calculation rules and traditional sources; it has not received an independently named professional review. Updated 27 October 2026. Compare the linked calculation records before relying on a boundary case.