Have fun determining the "exact" time since this dependes on...
many variables such as which processing center you file your I485 with, advertised processing date, how processing officers feel that day, how the economy performs, your application designation... etc.
I don\'t mean to give you a hard time... but I think that soon you will understand what a hard time we are all having to come up with the answer to your question.
Best of luck.
Alex