Sources and licenses
Every calculation on this site comes from open code and open data. This page lists each one, what we use it for and its license. Naming a project does not mean it endorses this site.
| What | Source | Used for | License |
|---|---|---|---|
| Positions of the Sun, Moon and planets; moon phases, eclipses, retrograde stations, sign changes | Astronomy Engine 2.1.19 by Don Cross | Every tool and every computed table | MIT License (Copyright (c) 2019-2025 Don Cross). The notice is kept in our code. |
| Houses (Placidus, Whole Sign, Equal), Ascendant, Midheaven, Vertex, Part of Fortune, mean and true node, mean Black Moon Lilith, Lahiri ayanamsa | Published formulas (Jean Meeus, Astronomical Algorithms; the Lahiri ayanamsa of the Indian Calendar Reform Committee, 1955), written in our own code | Chart tools | Mathematical methods; our code |
| Cities and their time zones | GeoNames, cities15000 (cities with more than 15,000 people) | Birthplace search | Creative Commons Attribution 4.0. City data © GeoNames (geonames.org) |
| Historical time zones and daylight saving time | IANA time zone database, used through your browser | Converting birth times to world time | Public domain |
| Fonts | Sora, Red Hat Mono, Noto Sans Symbols and Noto Sans Symbols 2 (subset), served from our own server | All pages | SIL Open Font License 1.1 |
| Site code | Astro (static site generator) | Building the pages | MIT |
Notes
- All astrology texts on the site are written by us. Reading texts, tarot meanings and numerology meanings follow public tradition in our own words.
- We do not use Swiss Ephemeris, JPL data or any commercial atlas.
- Time zone history before 1970 is less certain for many places; the tools warn about it and let you set the UTC offset by hand.