Astrology has no significance if it fails to judge the probable(suitable) time of events in the life of human beings. Sayana astrology which is popular in west make use progressed horoscopes for every year from horoscopes at birth.Effects of Transits of planets are discussed in all kinds of astrologies. One of the salient features which makes vedic astrology different from other systems of prediction is dasa systems. Vimsottari dasa system is the most popular and widely practiced. In this system maximum length of human-life is 120 years .This period is divided between 9 planets inluding Rahu and Ketu.The periods alloted for each planet is different. 27 Nakshatras(stars)into 3groups of 9 stars each of one group is ruled by a planet.The rationale of the order of planets executing consecutive dasas and the number of years allotted to each planet is discussed in detail in book HINDU DASA SYSTEM -by GRACE-INGLIS.Every planets period is again divided into 9 sub-periods and every sub period is again divided into sub-sub periods(120 years= 9X9X9=729 sub-sub periods).