There are 27 different schools of thought in Astrology. I use Nirayana System with true Lahiri Chitrapaksha ayanamsa which is used by most astrologers in the south. However these differences are primarily on account of different Ayanamsa being followed. Sayana System (Western Astrology) uses no precessions into account. In Scientific evaluation, whichever method you follow the strengths more or less remains the same. And the Mahadasa and Antardashas, you should read my article “Day to day predictions in Astrology” which will make you realise that the convergent effects of all planets do take place in each of our breath and the timings based on Dasas and antardasas are only an approximation.
How does it matter therefore whether you are now running Rahu dasa or Jupiter dasa. Anyway Jupiter dasa according to me starts only in Jan 2015.