How vimshottari dasha is derived

Vimshottari dasha rests on one thing — which nakshatra Chandra occupied at birth, and how far into that nakshatra it had travelled. Everything else follows from it: a 120-year cycle, nine graha, and a fixed share for each.

People treat dasha as a mystery. It is not — it is a division you can do on paper. The arithmetic is below.

Step one — Chandra's nakshatra

There are 27 nakshatra, each 13°20′ wide. Divide Chandra's sidereal longitude by 13°20′ — the number you get is the nakshatra. In our sample kundli Chandra sits at Dhanu 18°04′, which is Purva Ashadha, whose swami is Shukra.

Step two — how much is left

You do not get the first mahadasha in full. Whatever part of the nakshatra Chandra had already crossed is already spent. Multiply the remaining fraction by that graha's total years — that is your balance dasha.

The dasha tells you which graha is speaking. What it says comes from the kundli.

Step three — the sequence

The sequence is fixed and never changes: Ketu, Shukra, Surya, Chandra, Mangal, Rahu, Guru, Shani, Budh. You start at your first dasha and move through in that order. 120 years in total.

How to read it

The mahadasha tells you which graha is dominant now. Inside it sits the antardasha, and inside that the pratyantar. A practical way to hold it: mahadasha is the season, antardasha the month, pratyantar the day. When all three point the same way, the reading is clear.

One more thing — a dasha says nothing on its own. You have to read where that graha sits in the kundli. A Rahu mahadasha runs completely differently for two people, because Rahu sits in a different place in each kundli.