A Serious Question About "Time Traveling"...?

I have seen in shows (bad source to list) that people can hypnotize people, in a way, and they can relieve their past a bit. I want to know if that can be self-induced and how to do it. I want to see my great-grandparents again and remember their voices. They raised me, and I can't get over their deaths like I should and I want to see them again. Any help or even a name for the practice I am describing would be wonderful.