chronoagoraphobia
A fear of going into unfamiliar territory plus a fear of the vast nothingness between now and then equals a fear of time travel.
As Dext approached the swirling bright lights of the time machine, his heart beat fast, his head ached, and his mouth felt dry, as if he'd been in the desert for twenty years. His last bout with Chronoagoraphobia almost kept him from travelling back in time, but this time he ignored his fears and pushed onward.