I've experienced something like this programming in a room in the basement of a hospital at a medical imaging device for 8 hours, where notable project progress came in the course of days, not hours. With the absence of light, external stimulation, voices, or people, which would traditionally alert the mind to refocus on another stimuli and contextualize the stimulation against the time of day, the only alert is progress. To be clear, there is no mistaking the long period of time spent during the day whilst performing the mechanics of the task, but at the conclusion of the day, if there was no milestone of progress hit, and were it a day where there were literally zero interruptions, it would feel like I had only been down there 3 hours.