Jyotisha does not only describe a chart; it times it. The most widely used timing system is Vimshottari dasha (“of 120”), set out in Brihat Parashara Hora Shastra. It divides a 120-year life span into nine periods, each ruled by one graha.
The nine periods
The order and lengths are fixed. Each lord also rules three nakshatras, nine apart, and a Moon in any of them starts life in that lord’s dasha. The table is read from this site’s engine.
| # | Mahadasha lord | Length | Starts first for a Moon in |
|---|---|---|---|
| 1 | Ketu | 7 years | Ashwini, Magha, Mula |
| 2 | Venus | 20 years | Bharani, Purva Phalguni, Purva Ashadha |
| 3 | Sun | 6 years | Krittika, Uttara Phalguni, Uttara Ashadha |
| 4 | Moon | 10 years | Rohini, Hasta, Shravana |
| 5 | Mars | 7 years | Mrigashira, Chitra, Dhanishta |
| 6 | Rahu | 18 years | Ardra, Swati, Shatabhisha |
| 7 | Jupiter | 16 years | Punarvasu, Vishakha, Purva Bhadrapada |
| 8 | Saturn | 19 years | Pushya, Anuradha, Uttara Bhadrapada |
| 9 | Mercury | 17 years | Ashlesha, Jyeshtha, Revati |
The starting dasha and its balance
The first dasha is that of the lord of the Moon’s nakshatra at birth. But you are not usually born at the start of it. The portion of the nakshatra the Moon has already crossed counts as the part of the dasha already used up, and only the remainder — the balance — is left.
A worked example. Rohini spans 10°00′ to 23°20′ Taurus and is ruled by the Moon, whose dasha lasts 10 years. A Moon at 15° Taurus has crossed 5° of Rohini’s 13°20′ — 37.5% of it. The balance is the remaining 62.5% of 10 years: 6 years 3 months of Moon dasha. Mars (7 years), Rahu (18 years) and the rest follow in order.
Antardashas
Each mahadasha is divided into nine antardashas (sub-periods), in the same order, beginning with the mahadasha lord itself. Each sub-period’s length is in proportion to its lord’s share of 120:
antardasha = mahadasha years × antardasha lord’s years ÷ 120
In Saturn’s 19-year mahadasha, for example, the Saturn–Mercury antardasha lasts 19 × 17 ÷ 120 = 2.69 years — about 2 years 8 months.
Why the birth time matters
The Moon moves about 13° a day, so a two-hour error in birth time shifts it by about 1.1°. In a Venus nakshatra, where 13°20′ of Moon motion stands for 20 years of dasha, that is a shift of more than a year and a half in every dasha date that follows.
Conventions
- This site uses a 365.25-day year. Some astrologers use a 360-day year instead, which makes every later dasha start earlier — after 50 years, by more than eight months.
- The Moon’s position is sidereal, on the Lahiri ayanamsa. A different ayanamsa moves the Moon and so the balance.