Accuracy & Methodology

Every panchanga timing — Rahu Kaal, Yamagandam, Gulika Kaal, Brahma Muhurat — is derived from the actual sunrise at your city's exact latitude and longitude.

We use the Jean Meeus astronomical algorithm (the same standard used in modern ephemeris software) to compute sunrise to sub-minute precision. This is not an approximation. The calculation accounts for your city's latitude, longitude, and the sun's apparent altitude including atmospheric refraction.

This matters because sunrise in Srinagar is nearly 90 minutes earlier than sunrise in Port Blair. Panchanga timings calculated from a fixed national standard would be wrong for most Indian cities.

Vedic astrology uses the sidereal zodiac — fixed against the stars — rather than the tropical zodiac used in Western astrology. The conversion between the two requires an ayanamsa correction.

ShubhDivas uses the Lahiri (Chitrapaksha) ayanamsa, which is the official standard adopted by the Government of India's Calendar Reform Committee in 1957. It is the ayanamsa used by the overwhelming majority of traditional pandits and almanac publishers across India.

The ayanamsa value for any date is computed precisely using the known rate of precession of the equinoxes, anchored to a verified reference value at J2000.0.

The five elements of panchanga are computed from the Moon's and Sun's sidereal positions at any given moment:

• Tithi — the lunar day — is the angular separation between the Sun and Moon, divided into 12° increments. Each tithi ends when the Moon moves exactly 12° ahead of the Sun (sidereal).
• Nakshatra— the lunar mansion — is determined by the Moon's sidereal longitude, divided into 27 equal sectors of 13°20' each.
• Yoga— is the sum of the Sun's and Moon's sidereal longitudes, divided into 27 equal sectors of 13°20' each.
• Karana — is half a tithi (6° of Sun-Moon angular separation). There are 11 karanas, cycling through the lunar month.
• Vara — the weekday — follows the standard Vedic assignment of planetary rulers to each day, beginning at sunrise.

End times for each element are found by solving for when the Moon next crosses the relevant degree boundary, using iterative interpolation.

These inauspicious periods are traditional divisions of the day based on the classical Vedic planetary hour system. The day from sunrise to sunset is divided into 8 equal parts. Each part is approximately 90 minutes, but varies day by day as the length of daylight changes through the year.

Each day of the week has a fixed order for which of the 8 parts belongs to Rahu, Yama (Yamagandam), and Gulika. Because we calculate from the actual sunrise at your city, these windows are specific to your location and today's date — not approximations from a fixed table.

Moonrise and moonset are computed using the same Jean Meeus iterative rise/set algorithm used for sunrise. The Moon's position is interpolated across three consecutive days to account for its rapid motion (~13°/day), and the standard lunar altitude correction is applied. Times are accurate to within 1–2 minutes for Indian latitudes.

ShubhDivas supports nine regional panchanga traditions. All of them share the same Drik (observational) astronomical base described on this page — the tithi, nakshatra, yoga and kaal timings are identical across traditions. What each tradition selects is the regional dimension: which festivals are shown, their native-script names, and the regional calendar era (Saka, Bangla San, Kollavarsham, Vikram Samvat and so on).

The Tamil Thirukanithatradition — "thirukanitham" means true reckoning — is the same modern astronomical calculation as Drik. We do not offer a Vakya (classical table-based) variant, because reproducing its distinct tithi boundaries requires the full Sukra/Chandra Vakya tables; rather than mislabel Drik output as Vakya, we serve Tamil users under Thirukanitha.

If you find a timing that differs from your local pandit or traditional almanac, please email us at hello@shubhdivas.in with:

• The city and date
• Which timing or element differs
• What value you expected and its source

Discrepancies of up to 1–2 minutes are normal across different software, due to differences in ΔT tables and ayanamsa reference values. Larger differences will be investigated and corrected. Accuracy is non-negotiable for us — families rely on these timings for decisions that matter.