Daśā refers to planetary ruling periods used in Vedic predictive astrology. The Vimshottari system (120-year cycle) is most widely used: each planet rules for a fixed number of years (Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17, Ketu 7, Venus 20). The sequence begins from the nakshatra of the Moon at birth. Within a main dasha (mahadasha) are subdivisions called antardashas (sub-periods), which further subdivide into pratyantardashas.