How Vimshottari dasha works
The nine periods run in a fixed order over 120 years: Ketu 7, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19 and Mercury 17. Your birth star decides which period you were born into, and how far the Moon had travelled through that star decides how much of it remained.
Each mahadasha divides into nine antardashas (bhuktis). The free result shows the ones you are running now; the full report gives every date and what each period brings.