OPENJYOTISH PRIMER, CHAPTER 2: VIMSHOTTARI DASHA READING
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Original synthesis by the OpenJyotish contributors (AGPL-3.0, like the
program). Doctrine restated from the public-domain texts in this folder;
all dates below computed live by this program's Vimsottari engine —
reproduce them with `jhora dasa "1990-01-15 17:30:00 +0530 12.9716
77.5946"` before trusting a word.


1. THE 120-YEAR CYCLE
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Vimshottari ("120") unfolds life as nine planetary periods in fixed
order, always starting from Ketu:

Ketu 7, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16,
Saturn 19, Mercury 17. Total: 120 years (7+20+6+10+7+18+16+19+17).

At birth you enter the Mahadasha of the Moon's nakshatra lord — not at
its start but with the remaining balance (sesham): the untraversed
fraction of the nakshatra times the lord's full years. From there the
sequence runs forward through the cycle, wrapping from Mercury back to
Ketu if life is long. This program computes the balance from the exact
Moon longitude, never from rounded tables.


2. ANTARDASAS (SUB-PERIODS)
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Each Mahadasha subdivides into nine antardasas in the same lord order,
durations proportional to the sub-lord's years: within a Mahadasha of M
years, the antardasha of lord L lasts M × (L's years) / 120. So a
7-year Ketu Mahadasha contains a Ketu antardasha of 7×7/120 years
(about five months), while a 20-year Venus Mahadasha contains a
Venus–Venus portion of 20×20/120 years (about three years four months).

Rotation rule this program implements: antardasas begin from the
Mahadasha lord itself (Ketu Mahadasha opens with Ketu antardasha),
then follow cycle order. Deeper levels (pratyantardasa and below)
subdivide by the same proportion.


3. HOW TO READ A PERIOD
-----------------------
Mahadasha is climate, antardasha is weather. Judge every period by its
lords, in this order:

1. House placement from lagna: angular houses (1, 4, 7, 10) empower,
   dusthana houses (6, 8, 12) afflict, trines (1, 5, 9) bless.
2. Sign dignity: exalted, moolatrikona and own-sign lords deliver
   cleanly (see Primer Chapter 1); debilitated and inimical lords
   deliver late, partially, or through difficulty.
3. Yogas involving the lords: Dhana, Raja and Viparita combinations
   from Chapters 3 manifest most strongly when one of their planets
   runs its period.
4. The antardasha lord modifies the Mahadasha lord: friendly lords
   cooperate, inimical lords obstruct, malefics accelerate, benefics
   stabilize. Never read an antardasha alone — it always speaks inside
   its Mahadasha's sentence.
5. Transits trigger: a period's promise typically materializes when a
   slow transit (Saturn, Jupiter) aspects or joins the period lords
   (see Chapter 5).

What dashas do NOT do: they do not override the natal chart. A weak
house gives weak results even in its lord's best period; dashas time
the ripening, they do not plant the seed.


4. WORKED EXAMPLE
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Reference chart: 1990-01-15, 17:30 IST, Bangalore. Moon in Purva
Phalguni-4, whose lord is Venus — so life opens inside Venus Mahadasha
with the untraversed balance, computed by the engine as:

Venus 1990-01-15 → 1994-05-16 (birth balance, ~4.3 of 20 years)
Sun 1994-05-16 → 2000-05-15
Moon 2000-05-15 → 2010-05-16
Mars 2010-05-16 → 2017-05-15
Rahu 2017-05-15 → 2035-05-16 (18 full years)
Jupiter → 2035-05-16 → 2051 (follows Rahu)

Read Rahu Mahadasha for this Gemini lagna: Rahu's sign placement and
its dispositor's strength set an 18-year climate of ambition,
foreignness and unconventional rise, delivered through its
antardasas — Rahu–Rahu (2017-05-15 → 2020-01-26) rawest, Rahu–Jupiter
(2020-01-26 → 2022-06-21) guided, Rahu–Saturn (2022-06-21 →
2025-04-27) grinding, Rahu–Mercury (2025-04-27 → 2027-11-14)
intellectual and commercial, Rahu–Ketu (2027-11-14 → 2028-12-02)
severing. Each sub-period name, span and order above is engine output,
not illustration.


5. WHERE DASAS LIVE IN THE PROGRAM
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Dasas tab (interactive bar chart with current-period marker), `jhora
dasa` (full Mahadasha/antardasha tree), Dashboard (current MD/AD with
days remaining), conversation anchor (timeline the AI reads), and the
verification note (every dasa date in an AI answer is checked against
this engine before display).
