Methodology

How a Dasha90 reading is computed.

Written by the Dasha90 team · verified against a published reference dataset · last revised 30 August 2026

IN FIVE-YEAR-OLD WORDS

We do the maths very carefully with a real astronomy engine, check it against a trusted answer sheet, and only then let the words be written — and the words are never allowed to promise things or scare you.

The short version

We do the sky-maths with a serious astronomy engine, freeze the numbers, check them twice, and only then let the words be written. The words must point at the numbers they came from.

Dasha90 computes a sidereal (Lahiri) birth chart, the full Vimshottari dasha timeline, and a day-by-day scan of the next 90 days of transits using the Swiss Ephemeris. The computed facts are frozen into a packet, checked by an integrity gate, and only then interpreted in writing. The writing layer is not allowed to state anything the packet does not contain: every sentence in a report cites the computed fact IDs it rests on, and a validator rejects any draft that invents a degree, a date, or a forbidden claim.

Astrology itself has not demonstrated predictive power in controlled studies. What we promise is different and testable: that the traditional Jyotisha inputs are computed correctly, that the interpretation never exceeds those inputs, and that you can see the basis of every claim.

Conventions we fix in advance

These are our measuring rules — always the same ones, written down so anyone can check.

Zodiac and ayanamsha: Sidereal zodiac with the Lahiri (Chitrapaksha) ayanamsha — the convention used by most Indian panchangas. The ayanamsha is the angular offset between the tropical and sidereal zodiacs; around 2001 it is roughly 23°52′, and every report prints the exact value used for its chart.
Chart and houses: Rashi chart (D1) with whole-sign houses: the sign containing your ascendant is the whole first house, the next sign the second, and so on.
Nodes: Rahu is the true lunar node; Ketu is fixed exactly 180° opposite. The engine refuses to produce a packet where that opposition drifts.
Vimshottari year: The 120-year Vimshottari cycle is laid out with a year of 365.2425 days, and dasha boundaries are carried to the second rather than rounded to dates.
Time zones: Birth times are converted to UTC using the full IANA time-zone history for the birthplace, so a 1975 birth in Delhi and a 2001 birth in Delhi each get the offset that was actually in force.

The ephemeris

Our star positions come from a scientific engine that’s accurate to a tiny fraction of a hair’s width.

Planetary positions come from the Swiss Ephemeris, version 2.10.03, computed in its Moshier mode with speed terms enabled. Positions are accurate to well under one arcminute for the planets — far finer than the 13°20′ width of a nakshatra or the 30° width of a sign, and finer than the uncertainty introduced by a birth time that is off by even one minute.

Dashas, transits, windows

How we compute your seasons, the sky’s moves, and the dated boxes we call windows.

Vimshottari dasha: A traditional timing system that divides life into planetary periods. Your Moon’s nakshatra at birth fixes the starting lord and the elapsed fraction of that lord’s period; from there the mahadasha (major period), antardasha (sub-period) and pratyantardasha (sub-sub-period) chains are pure arithmetic. Dasha90 computes the full chain from birth and marks which periods are active during your 90 days.
Gochar (transits): The engine steps through each of the 90 days, recording sign ingresses, stations (a planet turning retrograde or direct, located by bisection to the day), Saturn and Jupiter’s houses as counted from both your Moon and your ascendant, and Sade Sati status.
Windows: Date windows in a report come from a fixed, deterministic rule table applied to those computed events — for example, Jupiter transiting the 5th, 9th or 11th from your Moon opens a supportive window. The writing layer must copy window dates verbatim; it cannot invent or move them.
Birth-time sensitivity: Your chart is recomputed at small offsets around your stated birth time (±1 minute for exact times, wider for rounded or approximate ones). Any fact that flips — ascendant sign, house placements, the Moon’s nakshatra — is downgraded to low confidence, and the report says so instead of pretending certainty.

How we verify the mathematics

We keep an answer sheet computed by other people’s tools. Before every release, our engine must match it — down to seconds.

The engine is pinned to a published reference dataset: a birth of 6 January 2001, 16:03 IST, Delhi, with longitudes, the ayanamsha, ascendant, nakshatras and the full dasha table cross-computed independently. An automated test suite asserts the engine reproduces that dataset — planetary longitudes to a small fraction of a degree, ayanamsha to the same precision, and dasha boundaries to the second — and the same assertions run against the live production engine on demand. Releases do not ship with these tests failing.

Before any words are written, an integrity gate re-checks each packet: the node opposition, the ayanamsha’s plausible range, that dasha spans nest and abut without gaps, that window dates fall inside the 90-day span, and that every fact ID a window cites actually resolves.

How the writing is constrained

The writing robot only gets our checked numbers. A second robot reads everything it writes and throws away anything that makes promises or invents numbers.

The interpretation is drafted by a language model that receives only the computed fact packet — never free rein. Three rules make that enforceable rather than rhetorical:

Citations: Every claim carries the IDs of the computed facts it is based on, and readers can open that basis in the report.
Validation: A validator rejects any draft that cites an unknown fact ID, alters a window date, states a degree figure not present in the packet, or touches a forbidden topic. A rejected draft is retried once with its violations attached; if it fails again, the order is marked failed and regenerated — an invalid reading is never shown.
Register: Claims are framed as tendencies that often correlate with a period — never as guaranteed events — and hedged claims say why (usually birth-time sensitivity).

What a reading never claims

We never talk about death, disease, babies, guaranteed money or marriages, court results, or being ‘100% accurate’. Ever.

The validator hard-blocks predictions about death or lifespan, disease, diagnosis or cures, pregnancy outcomes, guaranteed marriage, jobs, money or lottery results, legal outcomes, and any claim of “100% accuracy”. If you choose the health focus, the reading discusses energy and pacing only — it is not medical advice. Nothing in a Dasha90 report is medical, legal, or financial advice, and a reading is a lens for reflection, not a prediction of fixed events.

Change log

What changed on this page, and when.

30 August 2026: Methodology page first published, describing engine conventions as shipped.

Questions about a specific computation? Write to support@dasha90.in with your report link and we will show you the numbers behind it — or see the complete sample report first.