The Clockmaker (1953)
H.G. Tannhaus. He builds and repairs clocks and watches. A talented craftsman — and nothing more. He has not yet written a book about time travel. He has not yet built a mysterious apparatus. This changes when Claudia Tiedemann enters his workshop as an old woman and gives him a diagram.
The Clockmaker gets to work. It will be 33 years before he can activate his apparatus — with the help of a puzzling device that a man from the future, Ulrich, left behind in his workshop in 1953: a smartphone.