Ancient rules. Real sky.

Jyotish AI computes every Panchang element, festival date, muhurtham and kundli from the actual positions of the planets at your exact minute and place, then applies the rules of the classical Jyotish texts. AI is used only to explain the results in plain language. It never calculates anything.

Two layers: engine and AI

The app is built as two separate layers with a strict boundary between them.

Astronomy: where the planets are

Jyotish begins with astronomy. Before any rule can be applied, we need the exact longitude of the Sun, the Moon, the five visible planets and the lunar nodes (Rahu and Ketu) at a given instant.

Primary engine: Swiss Ephemeris

Our server runs the Swiss Ephemeris from Astrodienst, the reference library used by professional astrology software. It is based on NASA JPL planetary ephemerides and is accurate to about a thousandth of an arc-second. We use the official data files covering 1800 to 2400 AD.

Built-in engine for offline use

The app also has its own engine in JavaScript, so everything keeps working with no connection:

• Sun and Moon: the classical series from Jean Meeus, Astronomical Algorithms. The Moon uses the 50 largest periodic terms.
• Planets: NASA JPL's Keplerian orbital elements (Standish), converted from heliocentric to geocentric positions.
• Rahu and Ketu: the mean lunar node (the server also offers the true node).

In Auto mode the app uses the server when it is reachable and falls back to the built-in engine otherwise. A Compare engines tool in Settings shows the difference for any chart.

Time and place

A chart is only as good as its time. Most errors in astrology apps come from time zones, not from astronomy.

• Historical time zones: local birth time is converted to UTC with the IANA time zone database, which records every past change. That includes India's +6:30 war time in 1942–45 and US daylight-saving rule changes.
• Two places, two jobs: your birth place fixes your kundli forever. Your current city decides sunrise, Rahu kalam, festival dates and muhurtham. Born in India and living in the US is handled correctly.
• 196,000 places worldwide with coordinates and time zones, including small towns, searchable offline in the app.
• Sunrise and sunset are computed for your exact coordinates, with the standard 34′ of atmospheric refraction and the Sun's 16′ radius, the convention printed Panchangs use. A "Hindu sunrise" option (disc centre, no refraction) is available.

Sidereal zodiac and ayanamsa

Western astrology measures the zodiac from the spring equinox (tropical). Vedic astrology measures it from the fixed stars (sidereal). Because Earth's axis slowly wobbles (precession), the two drift apart by about 50 arc-seconds a year, roughly 1° every 72 years. The gap between them is the ayanamsa, currently about 24°14′.

Schools differ on the exact zero point, so the app supports several:

Offsets measured with Swiss Ephemeris; they stay constant to within 0.005° from 1950 to 2026.

Panchang and daily timings

The five limbs (pancha-anga) of the day all come from the Sun's and Moon's sidereal longitudes:

Start and end times are found by searching forward and backward in time until the value changes, then narrowing in by bisection. The server pins them to the second, the built-in engine to under a minute.

Daily windows

Festivals and the lunar calendar

Hindu festivals follow a lunisolar calendar, and the app builds it from scratch for your city:

1. New moons are found precisely, where Moon − Sun crosses 0°.
2. Months (amanta): each lunar month runs new moon to new moon and is named by the sign the Sun occupies at its start. When the Sun enters no new sign during a month, it is an Adhika (extra) month, as in 2026's Adhika Jyeshtha, and festivals are skipped in it.
3. The deciding time of day: a festival falls on the day its tithi is in force at the time the scriptures specify: sunrise: most festivalsmidday: Rama Navami, Ganesh Chaturthiafternoon: Dussehra, Raksha Bandhanevening (pradosh): Diwali, Dhanteras, Holika Dahanmidnight (nishita): Janmashtami, Shivaratri
4. Edge cases: a kshaya (skipped) tithi that never touches sunrise is assigned to the day it occurs. Raksha Bandhan avoids Bhadra (Vishti karana).
5. Solar festivals follow the Sun entering a sign (Makar Sankranti, Vishu, Baisakhi). Onam follows Shravana nakshatra in the solar month of Simha.

The monthly calendar can show Telugu/Kannada and Marathi/Gujarati (amanta) month names, North Indian purnimanta naming, or Tamil solar months, with the 60-year samvatsara name.

Kundli, dasha and strengths

• Lagna (ascendant) is computed from local sidereal time and latitude. Houses are whole-sign from the Lagna, the standard Parashari method.
• Divisional charts (vargas): D2 Hora, D3 Drekkana, D7 Saptamsa, D9 Navamsa, D10 Dashamsa, D12 Dwadasamsa and D30 Trimsamsa, by the Parashari division rules, with Vargottama detection.
• Vimshottari dasha: the 120-year cycle starts from the Moon's nakshatra. The balance at birth is proportional to how much of that nakshatra remains, and every mahadasha and antardasha is dated.
• Ashtakavarga: the complete bindu tables from Brihat Parashara Hora Shastra. The Sarvashtakavarga always totals 337, which serves as a built-in correctness check. Transit strength uses each planet's bindus in the sign it is crossing.
• Shadbala: six-fold strength: positional (uccha, saptavargaja, oja-yugma, kendra, drekkana), directional, temporal, motional, natural and aspectual, compared with each planet's classical minimum in rupas.
• Yogas and doshas: Gaja Kesari, Budhaditya, the five Mahapurusha yogas, Mangal dosha, Kemadruma, Kaal Sarp, Sade Sati and Dhaiya, each detected by its textual rule.
• Daily horoscope (Gochara): transits counted from your Moon sign using Phaladeepika's favourable-house tables, plus Tara bala from your birth star and Chandrashtama warnings.

Muhurtham, matching and more

Muhurtham

Every 15 minutes of each day is tested against all the classical filters together:

• Panchanga shuddhi: no Rikta tithi or Amavasya, a nakshatra approved for the event, no inauspicious yoga, no Bhadra, and a suitable weekday.
• Personal strength: Tara bala and Chandra bala from your birth star, and from both partners' for marriage.
• Kalas avoided: Rahu, Yama and Gulika kalam.
• Marriage-specific rules: Kharmas, and Guru or Shukra moudhyam (combustion).

Kundli matching

• Ashtakoota (36 gunas): Varna, Vashya, Tara, Yoni (the full 14×14 table), Graha Maitri, Gana, Bhakoot and Nadi, with the traditional cancellations.
• 10 Porutham for South India, with Rajju and Vedhai treated as essential.
• Mangal dosha for both partners.

Also built from the texts

Varshaphal (Tajika annual chart from the exact solar return, with Muntha, year lord and Mudda dasha) · Prashna (horary, judged from the chart of the moment the question is asked) · baby names from the Namakshar syllable of each nakshatra pada · tithi and nakshatra birthdays and Shraddha dates · remedies for planets that are weak in the chart or under difficult transits.

Where AI fits

AI is used for what it is good at, language, and kept away from what it is bad at, arithmetic and dates.

• Readings: the AI receives the engine's computed chart and rule findings and writes a readable explanation. Its instructions forbid recomputing or changing any position.
• Chat with engine tools: when you ask "When is the next Amavasya?" or "Good day to buy a car next month?", the AI calls the engine's tools (Panchang, festival search, muhurtham search, transits, dasha periods) and quotes the exact result. Each answer shows which calculations were used.
• Works without AI: the calendar, Panchang, festivals, muhurtham, charts and every rule-based reading run on your device. AI only adds the friendly wording.

AI provider: Anthropic Claude. Remedies are kept simple and traditional (mantra, charity, discipline), and the AI is instructed never to push expensive gemstones or pujas.

Accuracy and testing

The engine was checked against known references:

Built-in engine vs Swiss Ephemeris

Measured on a sample chart and day:

None of these changed a sign, nakshatra or pada in testing. Near a boundary the server's precision decides, which is why Auto mode prefers it.

Honest limits

• Shadbala omits the year and month lords and planetary war. Drik bala uses whole-sign aspects.
• The Varshaphal year lord is chosen from four of the five traditional candidates. Prashna uses Parashari rules, not KP or Tajika horary.
• Festival dates can differ by a day between traditions (Smarta vs Vaishnava, eclipse years). The app shows the rule used for each date.
• Predictions and remedies follow traditional texts and are offered for cultural and personal reflection. They are not medical, legal or financial advice.

Privacy

• Your birth details stay on your device. They are sent only to compute your chart (to our own server when it is available) and are not stored there.
• Anonymous usage statistics: a random ID created on your device, the screens you use, and your city help us improve the app. We never collect names, birth details, exact coordinates or the text of your questions. You can turn statistics off in ⚙ Settings.
• No advertising trackers and no selling of data.

Sources and credits

Software and data

• Swiss Ephemeris © Astrodienst AG, used under the GNU Affero General Public License v3. Server source: jyotish-ephe-server.
• GeoNames gazetteer (geonames.org), CC BY 4.0, the main source for city names and coordinates.
• countries-states-cities-database by dr5hn, ODbL 1.0, for supplementary places.
• IANA Time Zone Database for historical time zones, and tz-lookup (CC0) for mapping coordinates to time zones.
• NASA JPL, approximate Keplerian elements for the major planets (E. M. Standish).
• Jean Meeus, Astronomical Algorithms (2nd ed.).

Classical texts

Brihat Parashara Hora Shastra · Phaladeepika (Mantreswara) · Saravali · Muhurta Chintamani · Tajika Neelakanthi · the traditional Panchanga conventions of the Telugu, Tamil and North Indian calendars.