По версии Wikipedia:
The time frame of the series is never specifically addressed, but appears to be in the mid-to-late 1930s. The helicopter, television and jet engine are experimental devices, and most architecture is reminiscent of the Art Deco style of that period. In one episode, Baloo comments that "The Great War ended 20 years ago," suggesting that the series specifically takes place in 1938. Radio is the primary mass medium, and one episode even briefly alludes to the characters having never heard of television. http://en.wikipedia.org/wiki/TaleSpin#Synopsis

http://disney.wikia.com/wiki/TaleSpin Здесь почти тоже самое, чуть другими словами.

A вообще, согласен, что у них свой мир, который вне времени, как и в большинстве мультов.