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Why do birth charts differ?
Inspect time-zone resolution, house systems and a clearly labeled one-hour sensitivity comparison to understand chart differences.
Two chart results can differ because their inputs or conventions differ. This diagnostic makes the resolved UTC instant visible, compares house assignments and shows how an illustrative one-hour shift changes the Ascendant.
Place data: GeoNames geographical database,CC BY 4.0. Snapshot retrieved . The cities15000 directory does not include every settlement; manual coordinates and time zones remain available.
No name, email or account is needed. Your details stay on your device. Use the clear button to remove entered details and results.
How to use this tool
Enter the details exactly as recorded and select your intended house system. Compare the resulting UTC time and offset with another calculator before comparing interpretations. Check the local date, first or second clock occurrence, coordinates and zodiac convention.
How to read the result
Placidus and Whole Sign can assign planets to different houses without changing the Ascendant itself. A tropical-versus-sidereal difference is a different convention, not a one-hour clock error. The sensitivity example shows the consequence of changing an input; it is not an instruction to “correct” the recorded time.
Method and limits
This tool cannot establish which birth record or historical time-zone source is correct. It does not fetch, inspect or scrape another website’s private chart. Historical civil times can be uncertain, especially where the time-zone database lacks authoritative local records.
The calculation uses Astronomy Engine 2.1.19 and, where applicable, the project’s offline time-scale and house geometry modules. Mathematical positions and traditional interpretation remain separate.Read the full methodology.