The arithmetic of Vimshottari

Vimshottari carves a life into named periods. The word means "one hundred and twenty", and 120 years is all it has to give away.

Nine lords take fixed, unequal shares. Ketu gets 7 years, Venus 20, the Sun 6, the Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17. Add those up and you get exactly 120. Two of the nine, Rahu and Ketu, are not objects at all but two calculated points in the sky. The order never varies; after Mercury it returns to Ketu and begins again.

What makes one person's table different from anybody else's? One thing: where in the ring that life joins it.

That entry point comes from the moon. The same 360 degree ring that holds the twelve signs is also cut into twenty-seven equal arcs called nakshatras, each named after a star. Each arc is 13 degrees and 20 minutes of arc wide. A minute of arc is a sixtieth of a degree, not a minute of time. Every nakshatra is assigned one of the nine lords, three times round the list.

Find where the moon stood at birth. Its nakshatra names the first lord, and how far into that arc it had travelled tells you how much of that lord's term is left.

The essay works one made-up example. A moon at 123 degrees 20 minutes sits in Magha, whose lord is Ketu, who holds seven years. A quarter of that arc is spent, so three quarters of seven years remain: 5.25 years.

Then each big period, a mahadasha, is divided among all nine lords again in the same proportions: period length times the sub-lord's years, divided by 120. Those slices are antardashas. The nine inside Ketu's seven years add to exactly eighty-four months. That check takes a minute and catches real errors.

Two soft spots get named honestly. Some traditions count a year as 365.25 days and others as 360, which at the first boundary is four weeks of difference. An hour of doubt about your birth time moves everything by about three and a half months.