For the very pedantic, its T -79hrs 58min 30sec
Just moved from 6D to 4C on a 738 domestic flight and was shocked when the T-80 hr time slot produced no change to the seat map. It was only 1.5 minutes after the magic 80 hrs that the seat map opened up. It was quite stressful thinking that row 6 might be my destany for a 90 min flight