1940
See Wikipedia for what was happening around the world in 1940.
Here are some Old Time Radio episodes that aired in 1940:
Cavalcade of America
Jean Laffite
1940-02-06 (6.95 MB) [30:22]
Fibber McGee and Molly
Uncle Dennis Visits
1940-11-26 (6.81 MB) [29:45]
Jack Armstrong, The All-American Boy
Adventure Of The Sunken Reef Ep01 [Part 1 of 10] see more episodes
1940-12-23 (3.33 MB) [14:34]
Plus 13 more episodes locked away in the Random Dispenser!