The Perfect Time Machines

This story is a sort of fantasy. Sonam, the protagonist of the story eagerly listens to the talk of his grandfather and grandmother . He travels to someone's past and to the future.

But as the title,"The Perfect Time Machines " , what it could be?
How the protagonist makes his way to the past and the future?
Is there really a time machine in this story?

All the answers are just awaiting . Please do discover it.