When Does "Marvel Mystery Comics" #3 (1939) Take Place?

"Marvel Mystery Comics" #3 is a superhero comic-book written by Carl Burgos that released November 17th, 1939. So when is "Marvel Mystery Comics" #3 set?

It takes place on the fictional Marvel Universe in the year:

1939 AD

We know this because on the first page when Mr. Carson sees something shocking on a television news broadcast, he exclaims, "Great guns! - It can't be! It's impossible! This is still 1939!"

If one accepts the concept of the sliding timescale of the Marvel Universe, the events of this story might only take place at this point from its own point-of-view and they might move forward in time relative to new stories. Galactus, a god-like character with this fictional universe says in "The Utimates" #5 v2 that 'The present moment--the "now"--hurtles from past to future along a stream of events. And events have weight. Sometimes, the weight is vast--sometimes, so light as to be undetectable. But some events--those with a peculiar, unique gravity-- are caught by the present. Dragged in its wake, like planets about a sun. Always just a handful of years behind...' As Douglas Wolk wrote in 2021, "The big Marvel story is a funhouse-mirror history".

It is a chronologically midway comic in the Marvel Universe multiverse timeline and can be read at its timeline point after the previous issue, "Marvel Mystery Comics" #2 (1939).

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"Marvel Mystery Comics" #3 also includes the stories:

--The issue's first back-up feature is by Paul Gustavson with Ray Gill.