How we calculate your chart
Transparency matters in astrology. These are the exact methods and settings behind every chart on ZodiacGraph.
Planet positions
Positions of the Sun, Moon, planets and nodes are calculated with the Swiss Ephemeris, the high-precision astronomical library used by professional astrology software. Your birth time is converted to Universal Time using the historical time-zone rules of your birthplace (including past daylight-saving changes), and your birthplace is converted to coordinates using OpenStreetMap.
Zodiac, ayanamsha and houses
- Sidereal zodiac with the Lahiri (Chitrapaksha) ayanamsha — the standard in India and Sri Lanka.
- Whole-sign houses counted from the Lagna (ascendant) for all Parashari charts.
- Rahu is the true lunar node; Ketu is exactly opposite.
Divisional charts (Vargas)
We calculate all sixteen Shodashvarga charts from D1 to D60 using the classical Parashari rules, plus higher harmonics for advanced study. Every divisional chart uses the classical Parashari rule on the Lahiri ayanamsha — one method, the one traditional astrologers use.
Vimshottari dasha
The 120-year Vimshottari cycle starts from the nakshatra the Moon occupies at birth, with the balance of the first period calculated from the Moon's exact position. We show Mahadasha, Antardasha and Pratyantardasha periods; a dasha year is taken as 365.25 days.
Yogas, strength and transits
Yogas are detected from classical definitions; Ashtakavarga and Shadbala measure planetary strength. Transits (gochar) are calculated daily and mapped to your houses from both the Lagna and the Moon. Upcoming events in Today's Brief — sign changes, retrograde stations, eclipses and dasha changes — are computed from the ephemeris before any AI writes about them.
KP System
The KP tab is calculated separately, as the KP system prescribes: Krishnamurti ayanamsha, Placidus house cusps (Porphyry at extreme latitudes) and the mean node, with star, sub and sub-sub lords, significators and ruling planets. KP Horary uses the traditional 1–249 sub divisions of the zodiac.
How birth-time accuracy affects your chart
- Lagna (ascendant): changes sign roughly every two hours.
- Navamsa (D9) Lagna: changes roughly every 13 minutes.
- Shashtiamsa (D60) Lagna: changes roughly every 2 minutes.
- Moon sign and nakshatra: usually correct even with an approximate time.
If your birth time is uncertain, rely most on the Moon sign, nakshatra and dashas, and treat higher divisional charts with caution.
About Guru, the AI astrologer
Guru is powered by Anthropic's Claude models. It receives your calculated chart data — never raw guesses — and is instructed to answer from that data. Like any AI it can make mistakes, so treat its answers as guidance rather than certainty.