I read the book and watched the movie. I've heard people say that Colton imagined all of it because he was never technically "dead". I do not believe they have a clue at all. God is NOT bound by time, he created time as a measure for our lives.. thats all. Where God is there is no time. Colton could have been taken by the Lord for less than 1 second - and it would seem like months to Colton where he was. He could have spent YEARS there with the Lord.. and come back within that one second. It hard to wrap your minds around that, but its true.
Even the Word of God says this, while not a precise measurement it is meant to show you that time has no effect on Him. The Lord wanted Coltons story told.. so He arranged it.
"‘But do not forget this one thing, dear friends: With the Lord a day is like a thousand years, and a thousand years are like a day. The Lord is not slow in keeping his promise, as some understand slowness. He is patient with you, not wanting anyone to perish, but everyone to come to repentance.’ 2nd Peter 3:8