Vimshottari is the dasha system most Jyotish practice uses. The word means "one hundred and twenty" and that is the length of one full cycle.

Nine planets, fixed lengths

Each of the nine grahas holds a mahadasha of a fixed number of years, always in the same order: Ketu 7, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17. Add them and you get 120.

Neither the order nor the lengths change from chart to chart. The only thing your birth determines is where in the cycle you begin, and how much of that first period was already spent.

How your starting point is found

The 27 nakshatras are assigned to the nine planets in a repeating sequence, so each planet rules three nakshatras. The nakshatra your Moon occupied at birth gives you the planet whose mahadasha was running.

The proportion of that nakshatra the Moon had already crossed tells you how much of the period had passed. If the Moon was 40 per cent of the way through a nakshatra ruled by Venus, then 40 per cent of a twenty-year Venus period was already gone, and you were born with twelve years of it left.

This is why the Moon's exact longitude matters so much. A few minutes of birth time moves the Moon slightly, which changes the balance and shifts every subsequent dasha date.

The levels below

Each mahadasha subdivides into antardashas in the same nine-planet order, each proportional to its own length. Those subdivide again into pratyantardasha, and so on. Five levels is where most practice stops; the sixth level lasts a matter of hours.

Our calculator shows five levels and highlights the periods running now.

What a dasha is said to indicate

Traditionally, a mahadasha brings forward the significations of that planet as it sits in your particular chart — its house, its sign, its dignity, its aspects. The same Saturn mahadasha reads differently in two charts because the Saturn is differently placed.

This is why a dasha table alone says little. It tells you which planet is emphasised; the chart tells you what that planet means for you.

A caution

Dasha periods are frequently used to predict specific events on specific dates. There is no evidence supporting that, and the classical texts are considerably more careful than modern practice. Read a dasha as a change of emphasis, not as a calendar of events.