We almost missed our connection in DTW due to this problem. Flew SIN-NRT-DTW on Monday, and were elated when the big screen map data was showing arrival over one hour early. We set our watches to the time showing on the screen as "local time at destination". Our hope was to catch an earlier connection because of our early arrival. When we checked with a ticket agent in arrivals hall, we were informed that the flight was "closed". This should have been my first clue that our time was off, but in the fog of jet lag and a 14 hour time change, you don't think clearly. Off to the World Club where we dozed, munched, and sipped. I kept looking at my watch and cringing that we had so much time to kill. At some point I overheard CNN on a distant TV set and A. Cooper coming on, saying that it is 7:00 PM Eastern. What? My watch says 6:00 PM? Can this be true? I bolted to the front counter and asked the time. 7:00 PM. Holy sh**! We had a 7:19 departure many gates away in C. With adreneline waking us as we sprinted to our gate, we were greeted by name by the GA as the last two PAX to board our CRJ, the door shutting as we got onboard.

NW not only is negligent for not reprogramming these onboard flight data systems in a timely manner, but also in not pointing out that the data is incorrect and stressing the correct local time.