How your chart is computed — and exactly what leaves your device

The astronomy

Your birth date, time and place are converted, in your browser, into the geocentric ecliptic positions of the Sun, Moon and five visible planets, plus the Moon’s mean lunar node (Rahu, with Ketu placed exactly opposite it — standard Vedic practice, and what published panchangas and Vimshottari dasha tables are built on). This runs on astronomy-engine, an MIT-licensed, dependency-free library accurate to roughly one arcminute.

Those tropical positions are converted to sidereal — the fixed-star frame Jyotish uses, rather than the seasonal frame tropical Western astrology uses — with the Lahiri (Chitrapaksha) ayanamsa, referred to the true equinox of date. The ascendant (lagna) is derived from your local sidereal time, the birth latitude, and the ecliptic’s obliquity at that moment; houses follow the whole-sign system, the overwhelmingly standard convention in Jyotish, where each house is simply one full sign counted on from the lagna.

One arcminute of error is about 200 times smaller than the finest distinction a Vedic chart draws — a nakshatra pada, at 3°20′ wide. For the Moon, the fastest-moving body, that error corresponds to roughly two minutes of elapsed time, which perturbs a Vimshottari dasha balance spanning years by at most a few days.

How accuracy is checked

Astronomy libraries disagree with each other in ways that are invisible until someone checks. Every change to this engine is validated in continuous integration against Skyfield, an independently written, MIT-licensed library reading JPL’s DE421 ephemeris directly — a different implementation lineage from astronomy-engine, and one step closer to the primary source than Swiss Ephemeris itself. The check runs across roughly 200 birth moments spanning 1930–2020, both hemispheres and extreme latitudes: planetary longitudes must agree within one arcminute, and the derived sign and nakshatra must match exactly.

Worth being precise about the boundary of this check: it validates the astronomy — positions, sidereal time, the ayanamsa value — not the astrology on top of it. Nakshatra padas, house assignment, dasha arithmetic and compatibility rules are our own code, covered instead by dedicated tests and published-chart fixtures, and a Jyotish practitioner’s review of the interpretive layer is separate work again.

What never leaves your device

Your birth date, birth time, coordinates, UTC offset and name are never fields in any request this product makes, for any feature — not the free calculators at /tools, not a generated reading. The engine that computes your chart runs entirely as JavaScript in your browser; there is no server-side step that could see your birth moment even if one wanted to.

One exception, and it is the place name. Until 2026-09-20 a city index shipped with the site and the name never left the browser either. It now goes from your browser straight to a mapping provider, to turn it into coordinates — with no date, no time, nothing identifying you attached, and never through a server of ours. That is the whole of the change, and /privacy sets out what each party receives.

What is sent, and why — only when you ask for a reading

Every calculator on this site answers instantly with zero network requests. The one moment anything leaves your browser is when you ask for an AI-written reading, and even then what travels is a derived chart, not your birth details:

• your lagna, Moon sign and Sun sign;
• your nakshatra, its pada, and its ruling planet;
• each planet’s sign, house and degree — rounded to the nearest whole degree;
• each planet’s navamsa (D9) sign, computed from the unrounded chart in your browser;
• your current mahadasha and antardasha lord and end dates (never the exact start date — see below);
• a language tag, for the reading’s wording.

Explicitly and permanently absent: your name, birth date, birth time, birth city, birth country, coordinates, Julian day, UTC offset, time zone, account identifier, age and gender. The server that generates readings rejects any request carrying one of those fields outright — it does not silently strip it and continue.

Why positions are rounded, stated with the actual numbers

A chart precise enough to write a specific reading is, in a real sense, the birth moment expressed in another coordinate system — Jupiter and Saturn pin the year, the Sun pins the day, and the Moon, moving over 13° a day, pins the time. We measured this rather than assumed it: a chart sent at full precision let us recover the birth instant to within about one millisecond, and even a prompt written to two decimal places narrowed it to about a minute.

So planetary degrees are rounded to the nearest whole number before anything is sent, and no mahadasha is ever sent with its true start date — only the date it would have begun had it run its full canonical length, which is the true start for anyone past their first period and simply not their birth date for anyone still in it. Together, these bring the recoverable window to roughly nine minutes for someone who already knows your birth city — about six orders of magnitude tighter than where this started, and not zero. We would rather state that number plainly than round further and lose the dated, specific timing the readings are built on.

Your birth place is far less exposed than the time: positions are geocentric, so there is no parallax signal, and the lagna constrains place only to a longitude band thousands of kilometres wide.

The reading itself

Your birth date and time are used to calculate your chart in this browser and never leave this device. To turn the place name into coordinates, that name alone — with no date, no time and nothing identifying you — is sent from your browser to our mapping provider, never through a server of ours. The finished chart — planetary positions only, with nothing that identifies you — is sent to Google’s Gemini API to write your reading. We currently use Google’s free developer tier, which means Google may use that chart data to improve their models. Your name, your birth date and your location are never part of it.

Every model call goes through one internal interface, so the model that writes a reading today can change without changing anything about what leaves your device — and every response is validated against a strict schema before it is ever shown to you; we never treat free text from a model as trusted JSON.

Shared reading links

A shared reading link encodes a small, deliberately reduced summary of a reading directly in the link itself — a handful of chosen lines and a coarse, year-level view of one planetary period — rather than storing anything on a server. It never carries a lagna, a full chart, a birth date, a place or a name. Because the data lives in the link and nowhere else, sharing it is a one-way action: there is currently no way to revoke a link once it has been shared, so treat sharing one the same way you would treat sharing a screenshot.

Finding your birthplace

Place search runs entirely offline, against a dataset built ahead of time and downloaded to your device in small pieces as you type — no geocoding API, no key, no third party ever sees what you type into the birthplace field. Historical time-zone offsets (Sri Lanka’s and India’s changed more than once) are resolved against the full IANA time-zone database, not today’s offset, and the resolved offset is shown in the form so you can check it.

Place search by Geoapify (https://www.geoapify.com), data © OpenStreetMap contributors (ODbL).