Planetary data is public domain
Orbital periods, planetary radii, surface gravity, and moon counts are factual measurements published by NASA and other space agencies. Facts and measurements are not copyrightable. Anyone may use, republish, and compute with them freely.
The math is not copyrightable
The algorithms used here — Julian Day conversion, moon phase calculation, and the methods in Jean Meeus's Astronomical Algorithms — are mathematical formulas. Mathematics is not subject to copyright. The specific expression of the code is ours, but the underlying formulas belong to everyone.
Moon phases and orbital mechanics
The Moon phase on a given date is a deterministic astronomical fact. Computing and displaying it is no different from publishing a tide table or a sunrise time — it is factual information derived from public-domain physics.
NASA Astronomy Picture of the Day
When we display a NASA APOD image, we follow NASA's media usage guidelines. For images with a listed copyright holder, we show only a thumbnail-sized version with proper credit and a link to the official APOD page. For public-domain images (no copyright field), we display the image directly with attribution to NASA APOD.
Not astrology
This site does not practice astrology. Every calculation is grounded in real, measurable orbital mechanics and gravitational data. There is no claim that celestial positions influence human personality or events.
Your birth date
You providing your own birth date to a calculator that runs in your own browser does not implicate any third party's rights. The date is never stored or transmitted.
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