Dasha
every reader
What the tradition reads
Dasha names the whole family of Vedic timing systems that divide a life into consecutive periods, each ruled by one planet, so that the planet's own nature, dignity and house placement are read as most active and most visible during its own period. Several dasha schemes exist, keyed to different starting points, the nakshatra of the Moon, of the Sun, or of the ascendant among others, but the Vimshottari dasha, based on the Moon's nakshatra at birth, is by far the most widely used across the Vedic tradition and the one to which the term dasha most often refers without qualification. In the Vimshottari scheme a notional maximum life of one hundred and twenty years is divided among the nine grahas in a fixed order and for a fixed number of years each, so that the same planet always governs the same length of mahadasha, though which planet's mahadasha opens the life, and how much of its share remains, is set entirely by where the Moon stood within its nakshatra at the moment of birth. Each mahadasha is further divided into antardashas ruled by all nine planets in turn, so the dasha system in practice supplies not a broad decade of weather but a fine, layered calendar naming which planet's business is foremost at any given time.
The story
The Sanskrit dasha means a condition, a state, or a period, from a sense of something that has come to pass or now stands as circumstance, a term the tradition treats as naming the period rather than any planet within it. Wikipedia's account of the tradition records that the sage Parashara is credited with naming some forty two distinct dasha schemes, of which only two, Vimshottari and Ashtottari, remain in ordinary use, Vimshottari by far the more common of the pair and the one this glossary and the wider tradition mean by default when the word dasha appears without qualification. The same source notes plainly that it is not known when the Vimshottari system was first devised, nor why the number of years allotted to each of its nine planetary spans was fixed as it was, only that the total comes to one hundred and twenty exactly and divides without remainder among the nine grahas. The commencing mahadasha at birth is fixed by the lord of the janma nakshatra, the specific lunar mansion the Moon occupied at the moment of birth, so that two charts sharing a birth nakshatra can still open under different remaining fractions of that same lord's span. Vimshottari's dominance over Ashtottari and the tradition's other, now largely disused dasha schemes is a matter of long practice rather than an explicit ruling in any one text, and it remains the dasha taught first to any new student of Vedic astrology.
Written from
Corpus key glossary:dasha.