What Vimshottari dasha means

A 120-year cycle in nine unequal periods

Vimshottari is a timeline. It divides a notional 120-year lifespan among nine lords in a fixed order and with fixed lengths: Ketu 7 years, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17. Those nine add to exactly 120, and the order never changes.

The only thing that varies between two charts is where in that cycle you begin, and when.

Where your first period starts

Each of the 27 nakshatras is assigned one of the nine lords, cycling through the list three times. The nakshatra the Moon occupied at birth — the janma nakshatra — names the lord of your first mahadasha.

The length of that first period is prorated. If the Moon had already travelled 40% of the way through its nakshatra at birth, then 40% of that lord’s period is treated as already spent, and you begin with the remaining 60%. After that the cycle runs at full length, in order, and wraps around.

This is why the Moon’s exact position matters so much more than its sign alone: the fraction of one 13°20′ arc sets the start date of every period in the chart.

Sub-periods are the same proportions, again

Each mahadasha is subdivided into nine antardashas, and each of those into nine pratyantardashas. The rule is the same at every level: a sub-period takes the parent period’s total length multiplied by its own lord’s share of the 120 years.

So a Venus antardasha inside a Saturn mahadasha runs for 20/120 of that mahadasha. The structure is self-similar, which is why three levels are enough to locate any date quite precisely without inventing a fourth.

A dasha year is 365.25 days

One dasha year is treated as 365.25 civil days. This is a convention rather than an astronomical fact, and it is the convention most Indian software follows, so timelines here line up with what you would see elsewhere.

It is worth stating explicitly because it is exactly the kind of hidden constant that makes two programs disagree by weeks on a period boundary while both appear correct.

What a dasha is not

The computation above tells you which lord governs which stretch of time. It does not, by itself, tell you what any of that means — and this engine will not fill that gap by improvising.

Interpretation of a period comes from curated knowledge-base claims, cited inline. The source details show whether a claim is an internal draft or has been expert reviewed. Where the knowledge base has no claim covering a configuration, the reading says so instead of producing something plausible.