How We Calculate Panchang, Muhurat and Kundali

The positions of the Sun, Moon and planets come from the Swiss Ephemeris, a high-precision astronomical ephemeris based on NASA JPL data and used by most professional astrology software.

Vedic astrology measures positions against the fixed stars (the sidereal zodiac). We convert positions with the Lahiri (Chitrapaksha) ayanamsa, the standard adopted by the Government of India's Calendar Reform Committee in 1955 and used by most Indian panchangs.

The Hindu day begins at sunrise, so sunrise decides which tithi, nakshatra and festival belong to a day. We calculate sunrise for your exact latitude and longitude as the moment the upper edge of the Sun appears on the horizon, allowing for atmospheric refraction. This matches the convention used by Drik Panchang.

This is why the same festival can fall on different dates in India and North America.

A tithi is each 12° that the Moon moves ahead of the Sun. A nakshatra is each 13°20′ of the Moon's sidereal longitude. A yoga is each 13°20′ of the Sun's and Moon's longitudes added together, and a karana is half a tithi.

We find the exact moment each one ends by searching for the time the angle crosses its boundary, then convert it to your local time zone, including daylight saving time.

Each festival has a rule: the tithi it needs and the part of the day when that tithi must be present, such as sunrise, aparahna (afternoon), pradosh (evening twilight) or nishita (midnight). We apply these rules to the timings for your city.

North and South India name the lunar months differently (the purnimanta and amanta systems), so a festival's month name can differ between calendars even when the date is the same.

The time from sunrise to sunset is divided into 15 muhurtas, and so is the night. Abhijit is the 8th muhurta of the day (we skip it on Wednesdays), Brahma Muhurta is the 14th muhurta of the night before sunrise, and Nishita is the 8th muhurta of the night.

Rahu Kaal, Yamaganda and Gulika Kaal each take one of eight equal parts of the day, chosen by the weekday. Choghadiya and Hora also divide the actual day and night at your location, so their lengths change through the year.

The Lagna (ascendant) is calculated from your birth time and place. Divisional charts such as the Navamsa (D9) follow Brihat Parashara Hora Shastra, and Vimshottari Dasha periods start from the Moon's nakshatra at birth.

Kundali matching uses the traditional Ashtakoota (36-point Guna Milan) system with checks for Manglik dosha.

Our code has automated tests that compare our output with Drik Panchang for New Delhi, New York and Vancouver. They cover sunrise and sunset, tithi and nakshatra end times, festival and vrat dates, muhurat windows, Kundali planet and Lagna positions, and matching scores.

Timings must agree to the minute that Drik Panchang displays (muhurat windows within 2 minutes), and planet and Lagna positions within 1 arcminute. We run these tests whenever we change a calculation.

When a tithi ends within a minute or two of sunrise, panchangs can place it on different days. Regional solar calendars, such as the Tamil and Bengali calendars, also follow their own rules. If our date differs from your local panchang, follow your temple's custom and let us know so we can check it.