Every date on this site is an astronomical calculation, and every interpretation is a traditional reading built on top of it. This page documents both layers in full — the ayanamsa applied, how planetary positions are computed, the range and construction of the Saturn transit table, how retrograde re-entries are handled, and the weighting behind the severity score. It also states plainly what this site does not claim. If our dates ever disagree with another calculator, the explanation is almost always on this page.
Which ayanamsa is used?
This site uses the Lahiri (Chitrapaksha) ayanamsa, the standard adopted for Indian panchang calculation and the reference used by most Vedic astrologers in India.
The ayanamsa is the offset between the tropical zodiac used in Western astrology and the sidereal zodiac used in Vedic astrology; it is currently a little over 24 degrees and increases slowly over time. Because the offset is nearly a full sign, applying the wrong one can place a planet in the wrong rashi altogether. Any Sade Sati result calculated on tropical positions is measuring something different from what this site measures.
Different sidereal ayanamsas — Raman, Krishnamurti and others — differ from Lahiri by fractions of a degree. In practice that shifts Saturn’s sign-entry dates by a day or two, which matters only at the exact boundary of a phase.
How are planetary positions computed?
From the standard algorithms published by Jean Meeus in Astronomical Algorithms, implemented directly rather than through a third-party service. They are implemented directly on our server rather than fetched from a third-party service.
- The Moon is computed from a truncated version of Meeus’s lunar series, accurate to roughly one arcminute. This is far finer than needed for sign and nakshatra placement, and adequate for the pada level.
- The Ascendant is derived from local sidereal time, the birth latitude and the obliquity of the ecliptic, which is why a birth time and place are needed for the chart-level factors.
- The lunar nodes (Rahu and Ketu) use the mean node.
- Vimshottari dasha is derived from the Moon’s exact nakshatra position at birth, producing the full mahadasha and antardasha sequence.
All positions are then converted to sidereal by subtracting the Lahiri ayanamsa for that date.
How is Saturn’s transit table built?
From a pre-computed table generated with the Swiss Ephemeris, because Saturn’s transit dates are identical for everyone — only the natal Moon differs. Saturn’s position is not recomputed for each visitor, because it is the same for everyone.
| Property | Value |
|---|---|
| Date range | 1948 to 2072 |
| Sign-level windows | 104, retrograde re-entries preserved as separate windows |
| Nakshatra-level windows | 245 |
| Retrograde and direct stations | 239 |
| Resolution | Ingress moments solved by bisection to under one minute, then dated in IST |
Every boundary in the table is solved to the minute rather than estimated to the day, and each ingress is dated by the moment it actually occurs in Indian Standard Time — the convention Indian panchangs publish. Saturn’s entry into Pisces, for example, falls at 21:44 IST on 29 March 2025, which is why we date it to the 29th rather than the 30th.
The whole table — all 104 sign windows, 245 nakshatra windows and 239 stations — is generated from the Swiss Ephemeris using the Lahiri sidereal setting, and every window is checked back against it. The ayanamsa we apply matches the Swiss Ephemeris Lahiri value to within 0.001 arcminutes across 1900 to 2100. Where our dates differ from another site’s, the difference is in that site’s ayanamsa or its handling of retrograde motion, not in the astronomy.
How are retrograde periods handled?
Retrograde re-entries are preserved, not smoothed. This is the single most consequential decision in the engine and the most common source of disagreement with other calculators.
Saturn periodically appears to reverse direction. When it does so near a sign boundary it can leave a sign, move backwards into the previous one for several months, and then re-enter. During those months the transit genuinely pauses — the person is, for that period, no longer in the phase the calendar suggests.
Most calculators round this away and present one clean date range, which looks tidier and is wrong by up to four months. We publish the fragmented windows as they actually fall. A current example: Kumbha rashi’s setting phase runs from 29 March 2025 to 3 June 2027, stops while Saturn crosses into Aries, and resumes from 20 October 2027 to 23 February 2028. During that four-and-a-half-month gap, Aquarius Moons are outside Sade Sati.
If our dates differ from another site by a few days, the cause is usually the ayanamsa. If they differ by months, the cause is almost always smoothing. Why Sade Sati dates differ between websites covers this comparison in full.
How is the severity score calculated?
By weighing nine factors from your individual chart into a score from 0 to 100, where higher means more demanding. The severity score answers a question the dates cannot: two people share a moon sign and therefore share a cycle, so why is one having a harder time than the other? The score weighs nine factors from the individual chart and returns a number between 0 and 100, where higher means more demanding.
| Factor | Weight |
|---|---|
| Natal Moon strength — dignity, paksha, house, nakshatra, affliction by Rahu or Ketu | 20% |
| Natal Saturn’s dignity | 15% |
| Saturn’s functional nature for the Ascendant, on a five-point scale | 12% |
| Running mahadasha and antardasha | 12% |
| Natal Saturn’s house from the Ascendant | 10% |
| Benefic aspects on the Moon and Saturn | 8% |
| Malefic aspects and conjunctions | 8% |
| Current phase of the transit | 8% |
| Saturn’s transiting nakshatra against the Moon’s nakshatra lord | 7% |
The weighting is our own model. It is not a classical formula, and we state that plainly: classical texts describe these factors qualitatively rather than assigning percentages to them. What the model does is make a traditional judgement explicit and repeatable, so that the same chart always produces the same reading and every score can be broken down factor by factor.
How Saturn’s house from the Ascendant is scored. Saturn receives digbala — directional strength — in the 7th house, which classically makes it Saturn’s strongest placement, so the 7th reads as favourable here rather than difficult. The 10th is both an upachaya house and a kendra, and scores the same. The remaining upachaya houses — 3, 6 and 11, where Saturn is traditionally held to improve with time — follow, then the 9th. Houses 1, 2, 4, 5, 8 and 12 read as demanding. This is worth stating because several calculators treat every Saturn placement outside 3, 6 and 11 as adverse, which contradicts digbala and produces harsher scores than the tradition supports.
Three further constants, stated so that our results can be reproduced or disputed. Retrograde fragments separated by less than 400 days are treated as one continuous transit run rather than two cycles. The Moon is counted as afflicted by Rahu or Ketu within 12 degrees. Saturn is treated as combust within 15 degrees of the Sun.
Without a birth time, the Ascendant-dependent factors cannot be computed. Rather than redistributing their weight — which would produce volatile and often alarming scores — the engine runs a separate, deliberately conservative baseline model using five moon-sign-level factors, damped toward the centre of the range. A baseline score is labelled as such. Supplying a birth time typically lowers the score, because chart-level mitigating factors become visible.
Which tradition is used for Paya?
Paya, or Murti Nirnaya, is read once per cycle, from the Moon’s position at the exact moment Saturn enters the first Sade Sati sign — the 12th from the natal Moon. It does not change at the later phase boundaries. We resolve that ingress moment to under a minute rather than using noon on the ingress date, because the Moon travels roughly half a degree an hour and a twelve-hour approximation can land it in the wrong house. Counted from the natal Moon, and assigns the cycle one of four metals — gold, silver, copper or iron.
This site applies the Northern tradition, in which houses 1, 6 and 11 give gold; 2, 5 and 9 give silver; 3, 7 and 10 give copper; and 4, 8 and 12 give iron. Regional traditions differ on this mapping, and some South Indian traditions reverse the outcomes associated with gold and iron. Because the difference is real and unresolved, we state the tradition we use rather than presenting one mapping as universal — Sade Sati Paya explains the four metals and why traditions diverge, and the calculation logic is stored separately from the interpretive text so that regional variants can be offered without altering the underlying computation.
What this site does not claim
Four limits, stated directly.
- These are interpretations, not predictions. The transit dates are astronomy and can be verified against any panchang. Everything said about what a transit means is traditional interpretation within Vedic astrology, and interpretation is not evidence of outcome.
- Nothing here is medical, legal or financial advice. Where a reading touches health, money or legal matters it describes traditional associations. Decisions in those areas belong with qualified professionals.
- We do not prescribe gemstones. Gemstones sit last in the classical remedy hierarchy and are appropriate only for specific chart conditions. Recommending a blue sapphire because Saturn appears weak is not sound practice, and we do not do it.
- Severity is a model, not a measurement. The score is a structured, explainable judgement. It is calibrated to be internally consistent and transparent about its inputs; it is not a claim to have quantified anyone’s life.
Who calculates this?
By a small team, with the astronomical layer maintained separately from the interpretive one. The engine, the interpretive framework and the editorial content on this site are produced and maintained by the team described on our about page, which sets out who is responsible for the content and how it is reviewed. Corrections are welcome: if you find a transit date on this site that disagrees with a published panchang, tell us and we will check it against the table and publish a correction if we are wrong.
Sade Sati is a traditional system of interpretation within Vedic astrology. Transit dates on this site are astronomical calculations; interpretations are traditional readings, not predictions of outcome, and not medical, legal or financial advice.