Actual date. On my N-400, I put the actual start date, which was more than eight years prior to the date I filed my N-400. During the interview, my IO just asked me what I did for a living. Duration at employer didn't come up. If you put down just some arbitrary 5-year point, then you will not have answered the question truthfully. You have to certify at the end of the N-400, that you have answered every question on the form truthfully.
