Half A Day

At first look after reading this story, I felt very confused about what happened.  But when I let what had happened sink in I was a little creeped out.  Within this story we go from a five-year-old boy that struggles to keep up with his father turn into a possibly demented grandpa.  I know that some mysteries should be unsolved, but with this one, I am unsatisfied with what just happy; and in a way, I love it!  But what really confused me was the transition from out of the school to being old, because it seems that after the protagonist meets the guy that meets him outside he becomes old, but its not clear whether he is his father.  I am still a tad confused, but my overall reaction to this story is, "wow, that was cool."