How we calculate

Key facts

Zodiac

Sidereal (nirayana), not tropical

Ayanamsa

Lahiri (Chitrapaksha), 24°14′ in October 2026; adopted by the Government of India’s Calendar Reform Committee in 1955

Ephemeris

astronomy-engine (MIT licence), checked against the Swiss Ephemeris to within arc-seconds

Houses

Whole-sign bhavas; North Indian diamond chart

Rahu and Ketu

Mean node by default, true node as an option

Dasha

Vimshottari, 120 years, with a year of 365.25 days

Panchang

Calculated for the city’s coordinates; sunrise and sunset at sea level with standard refraction

Time zones

IANA time-zone database, with historical offsets

Answers

Ask JYOTISH and the reports are written by an AI writer, not a person, from the calculated chart and a classical rule book

The sky: how positions are calculated

Positions of the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn come from the astronomy-engine library (MIT licence). We compare it with the Swiss Ephemeris, the professional standard: the two usually agree within a few arc-seconds, and the worst cases are in the table below. Tropical longitudes become sidereal by subtracting the Lahiri ayanamsa for the exact moment, about 24°14′ in October 2026. Rahu and Ketu use the mean node, with the true node as an option. Sunrise, tithi, nakshatra, yoga and karana are calculated for your city and minute.

Accuracy, measured

Before every release we compare our engine with the Swiss Ephemeris (version 2.10.03, Lahiri, sidereal), the professional standard, at 3,000 moments chosen at random between 1940 and 2040, at random places on Earth. The table gives the largest difference we found for each, in arc-seconds; a degree has 3,600 of them.

What that means: the Moon moves about half an arc-second every second, so its largest difference equals about 16 seconds of birth time — finer than any recorded birth time. The lagna is within 0.5″, the Lahiri ayanamsa within 0.07″ of the Swiss value, and the retrograde flags agreed in 15,000 of 15,000 checks.

The tools are checked the same way. The muhurat finder’s day filter, written again from scratch, made the same choice on all 17,544 day-decisions; the panchang at sunrise matched on 102 of 102 days; Rahu kaal fell in the right part of the day 112 of 112 times; the Moon’s nakshatra and pada matched on 2,000 of 2,000 births; and the monthly rashifal’s transits matched the engine for all seven grahas. When your lagna sits within a degree of a sign’s edge, your kundali says so, because a few minutes of birth time can move it.

The tradition: how readings are made

Readings apply the Parashari tradition: Brihat Parashara Hora Shastra, Phaladeepika and Saravali for houses and yogas, the Vimshottari dasha for timing, gochar counted from the natal Moon, and Ashtakoot for matching. Houses are whole-sign: the rising sign is the first house and each following sign the next. The Vimshottari dasha runs 120 years in nine planetary periods, counted in years of 365.25 days from the balance left at birth. A jyotish scholar reviews our rule books.

Time and place

Birth time matters most: four minutes can change the lagna. The time zone comes from the IANA database with its history, so a 1975 birth is read with the zone rules of 1975. When the time is unknown, a Chandra (Moon) kundali is cast for noon, the lagna and houses are marked approximate, and the rashi and nakshatra are flagged if the Moon changed sign or star that day.

What the AI writer does and does not do

Ask JYOTISH and the written reports are produced by an AI writer, not a person. It works only from your calculated chart and our classical rule book. Every answer is checked against your chart before you see it; if a check fails, the answer is rewritten or replaced by the rule-based writer. The basis, the graha, house, nakshatra or dasha behind an answer, is printed separately, so you can check it with any panchang or astrologer. It does not promise outcomes, sell remedies, or stand in for a doctor, lawyer or financial adviser. A jyotish scholar reviews the rules and a weekly sample of answers.

The no-fear policy

We never predict disaster or ruin, and we never call a chart “bad”. Doshas are explained calmly, with the classical exceptions. We do not sell gemstones, pujas, yantras or remedies; a classical practice, when mentioned, is free and optional. There are no countdown timers and no hidden renewals, and the same rules apply to every visitor, whatever their caste, religion, gender or income. Read our promise.

What we do not claim

The astronomy is measurable. Whether planets shape human lives is a matter of tradition and belief, not proven science. So every page shows both layers apart, the calculation and the reading, and lets you judge. Results are for guidance and reflection, and nothing is promised.

To cite this page: SellnShip Solutions Pvt. Ltd., “How we calculate”, JYOTISH.info, checked October 2026.