Vimshottari dasha: calculating the planetary periods

Sequence and lengths

Nine periods (mahadashas) in a fixed order: Ketu 7 years, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17. Total 120 years.

Starting period

Each nakshatra has a lord in the same repeating order (Ashwini Ketu, Bharani Venus, Krittika Sun … Revati Mercury). The lord of the birth nakshatra gives the first mahadasha.

Balance at birth

fraction elapsed = (Moon longitude mod 13°20') ÷ 13°20'. Balance of the first period = (1 − fraction elapsed) × that period's years. Later periods run in full, in sequence.

Sub-periods

Each mahadasha divides into nine antardashas in the same order, starting with the mahadasha's lord. antardasha length = mahadasha years × antardasha lord's years ÷ 120. Antardashas divide the same way into pratyantardashas.

In Jyotishya

The current mahadasha, antardasha and pratyantardasha are shown with their start and end dates, using 365.25-day years. Results match the Swiss Ephemeris reference implementation.