Time travel is possible. Not in the future though; only the past.
It's because you don't set the destination with a dial; you set it with a memory.
The house you didn't live in long enough. The time you lost your best friend. The time you were too late to wave goodbye as your true love's train was leaving...
And you shouldn't change the past.
Because if you do, it'll smash the memory that was your anchor, and then you'll drift endlessly across time.