Vimshottari Dasha assumes that the maximum duration of life of an individual human being is 120 years which is the aggregate duration of all nine planetary periods i.e. Ketu 7, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19 and Mercury 17, in the order of their operation. In this system, the trine is the base used in calculations of planetary periods, that each trine begins with a Janma Nakshatra, and that a certain order was once visible in the sky (which order was also visible in the year 649 A.D. when 0 Degree of Aries sign very nearly coincided with Ashwini Nakshatra) the order in which the nine planetary periods or dashas operate. Hindus calculate their year on the basis of a Savan day of 60 ghatikas from sun-rise to next sun-rise, each ghatika is of 24 minutes duration, 30 Savan Days make one month and 360 Savan Days make one year. The year of the Vimshottari dasha is the Savan year of 360 Savan Days.