I'm just curious about when it first happened. At Marvel I think you can point to Fantastic Four #5 and say that was their first instance of it (Dr. Doom invented a time machine).
Anyone have an idea when the idea was first used in a DC comic? Did it happen often in the Golden Age or was it an idea you really saw more of in Silver Age stories?
Rip Hunter might have been the first one to make a career out of it starting in 1959, Showcase #20.
But the villain Per Degaton had a time machine back in 1947 in a story that has been referenced and followed up on many times, All-Star Comics #35.