We are 21st. Century and Astrology is a old science. On the same principals of our ऋषि मुनि. Can all the persons taken birth on say 15th, August, 1964 at 4.30 pm in Delhi will their fate or horoscope will be same no it can't be. Now the days Child Birth Rate is one child per second & we believe that no two human beings are same who have taken birth in this universe. So our first job is to fix the time. This we call BIRTH TIME RECTIFICATION now next calculate Sub-Sub lord.