How Jyotish Sarathi calculates a kundali

Step 1 — birth data and time zone

A chart begins with three inputs: date, clock time, and place. The place supplies latitude, longitude and the time-zone offset that was in force at that moment, which is what converts local clock time into the universal time the ephemeris is indexed by. Any location worldwide can be entered.

This is the single largest source of error in practice, and it is not a software problem: a birth time recorded to the nearest half hour moves the lagna by several degrees. If the time is uncertain, treat the ascendant, the bhava cusps and the dasha balance as uncertain too.

Step 2 — the computation method (siddhanta)

You choose how planetary longitudes are derived. The two options are genuinely different algorithms, not presets:

The full comparison of the two methods goes into how far apart the resulting charts land and which readings are sensitive to the choice.

Step 3 — ayanamsha (tropical to sidereal)

Modern astronomy reports tropical (sayana) longitudes measured from the vernal equinox. Vedic astrology needs sidereal (nirayana) longitudes measured from a fixed point in the zodiac. The ayanamsha is the offset between the two, and it grows by roughly 50 arc-seconds per year as the equinox precesses.

Jyotish Sarathi subtracts the ayanamsha you have selected — 11 or more systems are available, including Lahiri (Chitrapaksha), Raman and Krishnamurti. Different schools of jyotish disagree about the correct fixed point, and the disagreement between ayanamsha systems is usually larger than the disagreement between the two siddhantas, so this setting deserves a deliberate choice. See what ayanamsha is for the comparison.

Step 4 — charts, bhava and divisional charts

From the sidereal longitudes the app derives the lagna, the twelve bhava, and the divisional (varga) charts from D1 through D60 — Navamsha (D9), Dashamsha (D10), Trimshamsha (D30) and the rest. Charts render in both North Indian and South Indian styles; the underlying numbers are identical, only the drawing convention differs.

Step 5 — dasha, strength and yoga

• Dasha. Vimshottari, Yogini and Tribhagi systems, with Mahadasha, Antardasha and Pratyantardasha levels. The balance at birth comes from the Moon's exact position within its nakshatra, so it inherits the precision of the birth time.
• Planetary strength. Shadbala, with a dasha-bala table report.
• Ashtakavarga. Full bhava-wise strength evaluation.
• Yoga faladesh. 71 major yogas are detected from the chart, each with its own written interpretation.
• Matching. Ashtakoota (36 guna) Gun Milan with both charts and both dasha systems shown side by side.
• KP. Krishnamurti Paddhati sub-lord and cuspal analysis, which depends on fine sub-divisions and therefore on Drik Siddhanta positions.

Panchanga, patro and Vikram Sambat

Panchanga output — tithi, nakshatra, yoga, karana and vara — is derived from the same planetary longitudes as the charts, so the calendar and the kundali never disagree with each other. The Nepali patro adds festivals, auspicious timings and Rahukaal, and Vikram Sambat (BS) dates convert to and from Gregorian (AD) throughout the app.

What runs where

All astronomical computation runs locally on the device, from data bundled with the app. An internet connection is used only to look up birth-place data, install updates, and — if you explicitly enable it — sync saved profiles across your own devices. Birth details are not transmitted for a chart to be cast.

Known limits

Stated plainly, because a methodology page that lists no limits is not a methodology page:

• Charts outside 1768–2293 AD are outside the bundled ephemeris range.
• Surya Siddhanta positions drift relative to the observed sky, by design — that is a property of the classical algorithm, not a defect in the implementation.
• Historic time-zone and daylight-saving records are imperfect for some places and periods; an unusual historical birth time may need manual checking.
• Rectification of an unknown birth time is a judgement the astrologer makes. The software will not guess it for you.