How ParamJyotish calculates

Zodiac and ayanamsa

ParamJyotish works in the sidereal zodiac. The default ayanamsa is Lahiri (Chitrapaksha), computed as a mean value: a fixed value at a reference epoch advanced by mean precession, without short-period nutation. Raman and Krishnamurti (KP) ayanamsas are available in chart settings; each is a constant offset from Lahiri.

On 1 January 2000 the displayed mean Lahiri value is 23.852931°, while a true Lahiri value that includes nutation is 23.857084°, about 15 arc-seconds apart. Across 1850 to 2075 our Raman and KP values stay within 1 to 5 arc-seconds of Swiss Ephemeris.

Rahu and Ketu

Rahu is the true (osculating) lunar node, and Ketu is exactly opposite. The mean node, which some sites use, can differ from the true node by up to about 1°, enough to move Rahu into a neighbouring nakshatra pada or, near a boundary, a neighbouring sign.

Houses

Parashari charts use whole-sign houses: the rising sign is the first house and each following sign is one house. KP charts use Placidus house cusps, as the KP system requires, so a planet's KP house can differ from its whole-sign house.

Checked against Swiss Ephemeris

Planet positions come from Astronomy Engine (MIT licence), built into our Go calculation service. We compare a fixed test chart with Swiss Ephemeris; every difference below is a few arc-seconds, far smaller than the effect of a one-minute error in birth time.

Why might my chart differ from another site?

Most differences come from settings, not arithmetic. Check these four first:

True or mean node

We use the true node. A site using the mean node can place Rahu and Ketu up to about 1° away.

Ayanamsa

Raman sits about 1.44° behind Lahiri and KP about 5.5 arc-minutes behind, and “Lahiri” itself can be a mean or a true value. A different ayanamsa shifts every planet and the ascendant by the same amount.

House system

Whole-sign, equal, Sripati and Placidus houses can put the same planet in different houses even when its degree matches.

Time-zone source

Clock rules have changed over time: India, for example, kept war time an hour ahead between 1942 and 1945, and many countries use daylight saving. The IANA tz database records these rules; a site that applies one fixed offset such as +05:30 to every date can shift the ascendant by 15° for such births. Always check the UTC offset shown with the birth details.

Daily rashifal and “why today”

The public rashifal is a Moon-sign reading. For each IST date we take the sidereal Moon (Lahiri) at 12:00 IST and count houses whole-sign from each rashi to the Moon's sign. The day rating follows that Moon house. The reading opens with the Moon-house line and adds a focus sentence chosen by the weekday and by the tone of that rating (open for 4–5 stars, steady for 3, guarded for 1–2), so the reading changes every day even while the Moon stays in one sign for about two and a quarter days. The lucky number is a fixed function of the date and sign, so everyone sees the same result.

The “why today” line joins four traditional factors: the nature of the Moon's nakshatra (fixed, movable, fierce, mixed, swift, gentle or sharp, as grouped in classical muhurta texts), the tithi class (Nanda, Bhadra, Jaya, Rikta or Purna, with Amavasya on its own), the planet that rules the weekday, and the themes of the house the Moon occupies from your sign. The wording is our own.

Panchang and daily timings

Tithi, nakshatra, yoga and karana are taken at local sunrise for the chosen city, with the time each one ends. Rahu Kaal, Yamaganda and Gulika divide the daylight into eight equal parts by weekday; Choghadiya divides day and night into eight parts each; Abhijit is the midday window around local noon and is traditionally skipped on Wednesday.

Known limits

Birth time

The ascendant moves about 1° every 4 minutes and the Moon about 0.5° an hour, so an uncertain birth time matters far more than ephemeris precision.

One reading per day

The public rashifal uses the Moon at noon IST. If the Moon changes sign during the day, the evening may feel closer to the next day's reading.

High latitudes

Where the Sun does not rise or set, sunrise-based Panchang elements and daily timings are not shown.

Readings are traditional

Interpretations follow traditional Jyotish rules. They are not medical, legal or financial advice.

Calculation changelog