More like Twice Upon a Time

anchored on:science fictiontime travelmid 20th century

but

Narrow

October the First Is Too LateNovel
Fred Hoylestandalone novel1966
Science fiction and time travel, set in our world and mid 20th century.
The Proteus OperationNovel
James P. Hoganstandalone novel1985
Alternate history, tense in tone, about war.
The Lincoln HuntersNovel
Wilson Tuckerstandalone novel1958
Adventurous in tone, set in north america.
Operation Time SearchNovel
Andre Nortonstandalone novel1967
Science fiction and time travel, set in our world and mid 20th century.
“Snooping around a top-secret government installation, photographer Ray Osborne stumbled across an experimental time field.”
from the catalogue
The Black CloudNovel
Fred Hoylestandalone novel1957
Hard science fiction, tense in tone, about aliens and survival.
The Kraken WakesNovel
John Wyndhamstandalone novel1953
Alien invasion, tense in tone, about aliens and survival.
“Earth's life is disrupted by the attacks of extraterrestrials whose war machines, emerging from the depths of the oceans, seem indestructible.”
from the catalogue