Antar Dasha (Vimshottari)

Out of the 5 layers of Dasha, Antar Dasha is the 2nd layer. Then comes Pratyanter Dasha, Sukshma Dasha and Pran Dasha

All the planets have same sequence in Antar Dasha of each planet’s Mahadasha but each planet have different period of Antar Dasha. Each planet has its own Antar Dasha first followed by all other planets in sequence.

The sequence of Dasha is Sun, Moon, Mars, Rahu, Jupiter, Saturn, Mercury, Ketu and Venus.

Formula

Antar Dasha = 

        MD years of a planet x MD years of other planet (of Antar Dasha sequence)

 Total Vimshottari Dasha span

For example: Mahadasha is of Sun with its own Antar Dasha (Sun)

    So Mahadasha period = 6 years   

    Antar Dasha planet (M.D. years) = 6 years 

    Total Vimshottari Dasha span = 120

= 6 x 6     = 36     = 0.3  

    120    120

Hence Antar Dasha of Sun will be of = 0 years & 3 months in the Mahadasha period of Sun

Same rule applies for the Pratyantar Dasha and other layers of M.D.

(These are my study notes referred from Brihat Parashara Hora Shastra)