“Cosmic Corkscrew” was the first story that Asimov ever wrote for submission to the pulp
magazines of the day. In the first part of his autobiography, he describes starting the
story, setting it aside, and returning to it some thirteen months later. It was the story
that he took with him on his first visit to John Campbell, inquiring about why the July 1938
Astounding was late arriving. Alas, the story was rejected and then lost, but it did
have time travel!
In it, I viewed time as a helix (this is, as something like a bedspring). Someone could
cut across from one turn directly to the next, thus moving into the future by some exact
interval, but being incapable of traveling one day less into the future. (I didn’t know
the term at the time, but what I had done was to “quantize” time travel.)