Concept
Birth time correction: why the clock can mislead your chart
The hour pillar follows the sun at your birthplace, not the number on the clock. Correction is sometimes the difference between two different charts.
What the correction actually adjusts
Three separate effects sit between clock time and solar time: the historical timezone in force at your birth (including daylight saving, war time, and boundary changes), your longitude offset within that timezone (four minutes per degree), and the equation of time — the sun’s seasonal drift of up to about sixteen minutes. Our calculator applies all three and shows each number, so you can see exactly how far your clock time was from the sun.
Before and after: when it matters
If you were born at 14:58 near the western edge of a timezone, the corrected time may fall well before 14:00 solar — moving your hour pillar back one branch. Most births are not near a boundary and keep their pillar; the point is to know which case you are in, not to guess. The calculator flags boundary-risk births explicitly.
For two charts that already disagree, start with the calculator-disagreement audit. It identifies whether the difference comes from the source record, timezone, solar correction, solar-term instant or Zi-hour convention before any reading is compared.
Questions
Frequently asked
Usually, but not always. Clock time embeds your timezone and any daylight saving rule; the sun does not. Near an hour-pillar boundary, the corrected time can land in a different two-hour branch.
You can still compute year, month and day pillars — three quarters of the chart. Our calculator accepts an unknown time and simply omits hour-pillar readings instead of guessing.
Tens of minutes is common; at the far edge of a wide timezone, over an hour. China's single timezone spans what is geographically about five.
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