Ephemeris
Glossary · Last updated: 2026-07-26
An ephemeris (plural ephemerides) lists celestial positions for dates and times. Astrology software interpolates these tables to find sign boundaries.
Without an ephemeris or equivalent orbital math, sign calculators would rely on hard-coded date ranges that drift near cusps.
Our methodology
Western and Vedic positions on this site come from astronomical libraries with documented ayanamsa for sidereal work. See our calculator methodology hub for detail.