Open astrology calculation infrastructure and personalized birth chart tools

GetBirthChart builds developer-facing tools for reproducible astrology calculations and chart data. The platform combines deterministic astrology calculations, structured chart data, and evidence-grounded AI interpretations. The calculation layer is authoritative for computed chart facts: AI does not create planetary positions, houses, angles, or aspects. Interpretations are optional and should remain grounded in the supplied chart data and supporting evidence.

• Website
• Developer resources
• Methodology
• GBC Astro software
• Calculation validation
• Changelog
• How to cite

The gbc-astro-engine repository contains the Python calculation engine. Install the published package with:

pip install gbc-astro

from gbc_astro import calculate_chart

chart = calculate_chart(
    date="1990-05-15",
    time="09:30",
    latitude=51.5074,
    longitude=-0.1278,
    timezone="Europe/London",
)

print(chart.bodies["sun"].sign)
print(chart.angles["ascendant"].longitude)

The engine supports planetary positions and zodiac signs; Ascendant, Midheaven, and houses; aspects, orbs, and applying/separating phases; nodes and Chiron; synastry; transits, returns, and progressions; and explicit unknown-birth-time handling.

Birth details are normalized before calculation so that location, timezone, and chart settings are part of the computational context. Structured results preserve the inputs and relevant calculation metadata, making it easier to inspect, compare, validate, and cite outputs across applications. Public behavior is documented through the developer and methodology resources, while the changelog records meaningful changes over time.

An unknown birth time is handled explicitly. The engine does not silently replace missing time with an assumed value, and time-dependent outputs such as angles and houses are not presented as if they were known. When comparing results with another service, compare the full configuration as well as the displayed positions.

The calculation path is:

Birth details
    ↓
Location and timezone normalization
    ↓
Deterministic chart calculation
    ↓
Versioned structured chart
    ↓
Evidence selection
    ↓
Optional AI interpretation

For release and research context, see the Zenodo record and DOI. The engine also includes a CITATION.cff. The gbc-astro package is licensed under AGPL-3.0-only. Swiss Ephemeris has separate licensing and redistribution terms; review the engine's notices before distributing software or ephemeris data.

Astrology calculations and interpretations are provided as software and informational tools. Nothing here claims that astrology is scientifically validated.