A birth chart shows what a life contains. Dasha shows when. Vimshottari is the most widely used of the dasha systems, and it divides a notional 120-year lifespan among the nine planets in fixed proportions.
The nine periods
- Ketu — 7 years
- Venus — 20 years
- Sun — 6 years
- Moon — 10 years
- Mars — 7 years
- Rahu — 18 years
- Jupiter — 16 years
- Saturn — 19 years
- Mercury — 17 years
They always run in that order and always total 120. Which one you begin with is decided by the nakshatra the Moon occupied at birth, and how far through that nakshatra the Moon had travelled decides how much of the first period was already spent before you were born.
Three levels, not one
The mahadasha is the major period, running from six to twenty years. Inside it, each of the nine planets takes a turn as antardasha, in the same order and in proportion. Inside that, the same division happens again as pratyantar. A specific event is usually read at the antardasha level, with the pratyantar narrowing it to a window of weeks.
How a period is judged
A dasha lord delivers according to what it rules and where it sits in the chart. A planet ruling the 10th and placed strongly gives a period of professional advance; the same planet ruling the 6th and placed in the 8th gives a period of obstruction in that area. The combination matters more than the planet's general reputation — a well-placed Saturn period is often the most productive stretch of a life.
Reading a transit against a dasha
Transits and dashas answer to each other. A favourable transit during an unfavourable dasha usually produces an opportunity that does not convert; an unfavourable transit during a strong dasha produces a difficulty that is absorbed. When people say timing was right, they generally mean the two agreed.
Sade Sati arriving during a strong dasha and the same Sade Sati during a weak one are not the same seven and a half years.