when to start elf on a shelf

Well, as a Christmas Elf, I can tell you that the tradition of Elf on a Shelf started in 2005, when a children's book called "The Elf on the Shelf" was released. In the story, a scout elf is sent from the North Pole to a child's home to keep an eye on their behavior and report back to Santa. The elf is invisible to adults but is visible to the child, and he is assigned to the child for the holiday season.