How does the time or place switch around during Bud, Not Buddy by Christopher Paul Curtis? How does this switching serve the story?

The events of the story take place in chronological order over a period of a few weeks.  The time period is during the Great Depression, and the location is Michigan.  The story begins in Flint, Michigan, and it ends in Grand Rapids, Michigan.  The reason that the setting changes is because Bud is travelling across the state in order to find his father.  He succeeds in finding his grandfather.  

The only time that the story breaks away from the day-to-day narration of Bud's adventure is when the story does a flashback to a time when Bud's mother was still alive.  The flashback does a great job of showing readers how strong and passionate a woman Bud's mother is.  She cares deeply for Bud's welfare and wants to impart strong morals on him.  The flashback also explains why Bud always introduces himself as Bud, not Buddy.  His mother named him Bud, and she told him that Buddy was a name for a dog; therefore, his name was Bud, not Buddy.