The first time is occurred it lasted about 5 minutes; it could not have been any longer. In the moment however, he could have sworn that the feeling lasted a good portion of the day. A residual effect of the brain trying to understand what was happening was a good conclusion. There were of course several words for it that did not do it justice, but it was a good starting point to finding out what was happening to him. Derealization/depersonalization In short, he would describe the feeling as the world around him was not real. He was not real; his reality was false, frozen in time as everything slowed to a glacial pace.
Everyone supposedly has this same experience at some point in their lifetime. Most people get lost in thought pertaining to one's existence where they have an 'existential crisis'. What he experienced was much worse. A dream seems real when you are in it, you may not know exactly where it started but the world is real and you go with the flow of the world that your brain has created for you. Lucid dreamers would argue that they do in fact know that they are dreaming and can control the world around them. In either case the reality of the situation is that you are in a world that at the time is very real until the dreamer awakens back to his or her life. The dream felt entirely more real than when he had these Derealization occurrences.
Whenever it happened he quickly felt two things simultaneously; primal fear and the extreme lack of understanding of what was happening to him and around him. 2 hours was the duration of the last occurrence. Every grounding technique stopped working; he knew it would be over when it was over. The thing about it was each time it happened it lasted a little longer than the previous episode. Reality was losing a fighting battle in the recess of his mind and instead created a unique purgatory for him to exist. Isolation was a friend, a companion he could always count on when the occurrence took over. Ambivalence followed by apathy came after which lasted until the next season or until a good feeling/thought came knocking at the door like an old friend reconnecting after some time apart.
The problem with having been diagnosed with mental illness is that it never is just one symptom, but several that collimate into something that will always be a part of you.