At first glance I thought this sentence had a literal but poor English translation. I couldn't imagine a situation where you'd say this over, "When does dad come HOME?" I came to comments looking for answers but found none. (Please remember that children also use Duolingo, so please keep adult comments veiled rather than explicit.) However, I came up with the situation on my own: Your parents are divorced and your dad regularly picks you up on this day of the week, but you never remember when, hence, "When does dad come?"