Shashtihayani Dasha

The odd one in the family

Shashtihayani — shashti-hayani, “of sixty years”, and also called Shashti Sama — is a conditional nakshatra dasha whose cycle runs just 60 years. That alone makes it unusual: it is half of Vimshottari and barely more than half of its nearest sibling.

But the length is not what makes it interesting. Shashtihayani is the only one of the conditional nakshatra dashas that does not step one lord per nakshatra. It uses contiguous blocks instead — and that single structural fact changes how the starting lord is found, how the balance at birth is measured, and how sensitive the whole timeline is to your birth time.

If you read only one thing on this page, read the block section.

The eight lords and their years

Three lords of ten, five of six: 30 + 30 = 60. There is no gradual progression here — no run of consecutive integers, no doubling. Just two tiers, and a clean split of the cycle between them.

The lord list is the seven visible grahas plus Rahu. Ketu holds no period. Rahu takes the last block and closes the circle.

Blocks, not steps — the thing that makes this system

Here is the structural fact, stated as plainly as it can be.

Every other conditional nakshatra dasha — Dwadashottari, Panchottari, Shatabdika, Dwisaptati, Shodashottari — walks the zodiac handing the next lord to the next nakshatra. After one turn of the cycle it starts over, so each lord ends up owning three or four nakshatras scattered around the circle. Vimshottari does the same: Ketu owns Ashwini, Magha and Mula, a third of the zodiac apart each time.

Shashtihayani does not. Each lord owns one contiguous run of nakshatras, and the cycle goes round exactly once:

One pass, eight blocks, no repeats. The blocks run in the same order as the dasha sequence, which the stepping systems cannot manage — their sequence and their nakshatra map necessarily disagree once the cycle wraps.

Among the nine nakshatra dashas AstroShruti computes, only Ashtottari is built the same way. Shashtihayani is the only conditional one that is.

Why this changes the balance at birth

This is not a cosmetic difference. It changes the arithmetic.

In a stepping system the first Mahadasha’s elapsed fraction is measured across a single nakshatra — a 13°20’ arc the Moon crosses in roughly a day. In Shashtihayani the engine walks back to the first nakshatra of the lord’s block, measures the block’s full arc, and prorates across that:

• A three-nakshatra block spans 40° — the Moon takes about three days.
• A four-nakshatra block spans 53°20’ — about four days.

So a Moon in Chitra is not 20% through Chitra for Shashtihayani’s purposes; it is however far it has travelled from the start of Purva Phalguni, the Moon block’s first nakshatra, as a fraction of the block’s whole 53°20’. That could be 85%, giving a Moon balance under a year where a stepping system would have given several.

Two useful consequences fall out of this:

• Shashtihayani is less brittle at nakshatra boundaries. A Moon a few arc minutes from the Chitra/Swati line changes its Vimshottari lord entirely if the ayanamsha shifts. In Shashtihayani that same boundary is inside nothing — it is a block boundary only at the seven places the blocks actually change hands.
• But it is not insensitive. The fraction still moves continuously with the Moon’s longitude, so an exact birth time is still required, and the dates still move with the ayanamsha. A softer dependence is not no dependence.

The blocks are not equal

Three and four are not the same number, and the blocks come in both sizes: Jupiter 3, Sun 4, Mars 3, Moon 4, Mercury 3, Venus 4, Saturn 3, Rahu 3 — 27 in all. The Sun’s four-nakshatra block spans a third more sky than Jupiter’s three, yet both lords hold ten years.

There is no clean rule making a lord’s block proportional to its period. Rahu’s six years get three nakshatras; Mars’s ten years get three as well. The block map and the year table are two separate classical facts, and the engine stores them as two separate tables because that is what they are.

The missing Abhijit

The block counts above are not quite what the classics describe, and the gap has a name.

Classically, Shashtihayani’s blocks are counted over 28 nakshatras — the usual 27 plus Abhijit, which sits between Uttara Ashadha and Shravana. With Abhijit in the count, Saturn’s block is four, and the tally comes out 3-4-3-4-3-4-4-3.

AstroShruti’s map has 27 entries and Abhijit is not one of them. The engine’s nakshatra scheme divides the zodiac into 27 equal 13°20’ arcs, which is the scheme every other part of the app speaks — the Moon’s nakshatra, the padas, the KP star lords, the whole nakshatra reference. Abhijit does not occupy an equal 27th of anything; it is an unequal 28th carved out of the boundary region. A Moon therefore never lands in it, because in this coordinate system it does not exist.

The visible effect is exactly one nakshatra wide: Saturn’s block is Shravana through Shatabhisha, three nakshatras, where a 28-fold count would open it at Abhijit and make it four. Saturn’s years are unaffected; only the doorway is narrower.

We are telling you this rather than rounding it away because it is a real divergence between the shipped table and the classical description, and you would be right to notice it.

Sub-periods

Each period divides into the same eight lords, in proportion, starting from the parent’s own lord:

child_years = parent_years × lord_years ÷ 60

Inside the 10-year Jupiter Mahadasha, the Jupiter Antardasha runs 10 × 10/60 ≈ 1.67 years and the Moon Antardasha runs 10 × 6/60 = 1 year. Each Antardasha splits eight ways again, five levels deep: Mahadasha → Antardasha → Pratyantardasha → Sookshma → Prana.

Note that the block structure applies only at the top. It decides which lord opens your timeline and how much of that first period is already gone. Once the sequence is running, the sub-periods are the ordinary proportional split — identical in form to every other nakshatra dasha.

The CLASSICAL vs EQUAL setting changes nothing here. For nakshatra dashas the proportional split is the classical rule; both settings compute the same dates. The setting exists for Naisargika, Kala and the six Jaimini rashi dashas.

Sixty years is short

Worth flagging, because it has a practical consequence you will see in the app.

At 60 years the cycle turns over twice within a normal long life. AstroShruti generates the timeline to span at least 120 years from birth, so a Shashtihayani timeline shows each lord twice — a second Jupiter Mahadasha, a second Sun, and so on. That is correct and intended, not a duplication bug. For the short cycles it is also necessary: without repeating, an older native’s current period would simply fall off the end of the list.

When Shashtihayani applies

The classical condition is the simplest in the family: the Sun in the Lagna — the Sun tenanting the rising sign of the birth chart.

No divisional chart is needed, unlike Dwadashottari’s Venus-owned Navamsa Lagna, Panchottari’s Cancer D-12 Lagna or Shatabdika’s vargottama test. You can check it by looking. There is also a certain internal coherence to it: a Sun-marked chart gets the system in which the Sun holds one of the three long blocks.

Applicability is advisory. The engine computes Shashtihayani for every chart unconditionally; the interpretation layer flags whether your chart meets the condition. The dasha is never withheld and its relevance is never assumed.

What we do not compute

• We do not model Abhijit. The nakshatra map is 27-fold, so Saturn’s block is three nakshatras rather than the classical four. This is a known, deliberate divergence — the alternative would be an Abhijit that exists in one table and nowhere else in the app.
• We do not enforce the Sun-in-Lagna condition. It is flagged, not gated. A Shashtihayani timeline for a chart with the Sun in the 7th is arithmetically correct and classically off-label, and the app will say so.
• We do not offer a variant block map. The Ashwini-seeded arrangement follows the PyJHora baseline, the same source as the app’s other conditional dashas. There is no setting for an alternative grouping.
• We do not apply the block structure below the Mahadasha. Sub-periods are the plain proportional split. Any classical rule making the drill block-aware is not something we have implemented or claim to.
• We do not interpret the periods. A Rahu Mahadasha names a graha, not an outcome — that depends on Rahu’s house, its dispositor and the transits running meanwhile.
• We do not give Ketu a period. It holds none in this system.
• We do not reconcile Shashtihayani with Vimshottari. They will disagree, and at 60 versus 120 years they will disagree often. The app shows both and blends neither.

Notes on this timeline

• The cycle totals 60 years across eight lords — the visible grahas plus Rahu; no Ketu — in the order Jupiter, Sun, Mars, Moon, Mercury, Venus, Saturn, Rahu.
• Three lords hold 10 years each, five hold 6 each.
• Uniquely among the conditional nakshatra dashas, lords own contiguous blocks of nakshatras, counted forward from Ashwini, in one pass.
• Blocks are 3 or 4 nakshatras long — 40° or 53°20’ — and the balance at birth prorates over the whole block, not one nakshatra.
• The engine’s map is 27-fold; Abhijit is omitted, which costs Saturn’s block one nakshatra against the classical account.
• The starting lord and balance come from the Moon’s sidereal longitude, so the dates move with the ayanamsha.
• A dasha year is 365.2425 days, matching Jagannatha Hora and common software.
• The timeline spans at least 120 years from birth, so the 60-year cycle runs twice.
• Drilldown goes five levels: Maha → Antar → Pratyantar → Sookshma → Prana.
• Applicability — the Sun in the Lagna — is advisory. The dasha is always computed.