Planetary Ruler Calculator
Find the planetary ruler for a given date/time (planetary hour), day of the week, or zodiac sign using classical Chaldean order and modern astrology.
Formulas Used
Day Ruler: Each weekday is assigned a planetary ruler based on the Chaldean order (Saturn→Jupiter→Mars→Sun→Venus→Mercury→Moon). The ruler of each day is the planet governing its first hour: Sun(Sunday), Moon(Monday), Mars(Tuesday), Mercury(Wednesday), Jupiter(Thursday), Venus(Friday), Saturn(Saturday).
Planetary Hour Ruler:
- Sunrise is computed via the NOAA simplified solar algorithm using Julian Day Number, solar mean longitude, mean anomaly, ecliptic longitude, solar declination, and the hour-angle formula:
cos H = (cos 90.833° − sin φ · sin δ) / (cos φ · cos δ) - Day is divided into 12 equal hours of length
daylight / 12; night into 12 equal hours of length(24 − daylight) / 12. - The ruling planet for hour n (1-based) =
CHALDEAN[(dayRulerIndex + n − 1) mod 7]
Zodiac Sign Ruler: Classical rulers follow traditional Hellenistic astrology (Mars, Venus, Mercury, Moon, Sun, Mercury, Venus, Mars, Jupiter, Saturn, Saturn, Jupiter). Modern rulers substitute Pluto (Scorpio), Uranus (Aquarius), Neptune (Pisces).
Assumptions & References
- Sunrise/sunset uses the NOAA simplified algorithm accurate to ±1–2 minutes for latitudes between −65° and +65°.
- Time input is treated as local solar time (not timezone-adjusted clock time); for precise results, convert your clock time to local solar time using your UTC offset and longitude.
- Chaldean order source: Vettius Valens, Anthologiae (2nd century CE); Ptolemy, Tetrabiblos.
- Modern sign rulers (Uranus, Neptune, Pluto) per 20th-century astrological consensus.
- Polar regions (|latitude| > 65°) may produce inaccurate sunrise/sunset times.
- Reference: NOAA Solar Calculator — https://gml.noaa.gov/grad/solcalc/