Updated novels?

Having several times enjoyed the 1941 movie “The Maltese Falcon”– with its classic performances by Humphrey Bogart, Peter Lorre and Sydney Greenstreet– while at the same time being rather confused by the plot, I recently read the source for the film: Dashiell Hammett’s detective novel of the same name, a 1961 paperback edition of which I picked out of someone’s trash a few years ago.

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Of course the book includes incidents and references which would have been impossible to get past the film censors of the era. But the book and the movie tell the same general story, and I thought I had it pretty much figured out until the end, when (as is the norm for such novels) there was a rush to Reveal All and I was once again confused.

But that’s not why I’m posting. Rather it has to do with a story detective Sam Spade tells his client/lover Brigid O’Shaughnessy (on page 49 of my edition) about events which occurred, in a previous case he had investigated, in 1942 and 1947. Now there would be nothing exceptional about this, except that “The Maltese Falcon” was originally published in 1930. Since there’s nothing particularly futuristic about the novel (no flying cars or anything), I can only assume that those dates were different (most likely 1922 and 1927) in the original. According to the title page of my paperback, it’s a second printing of an edition of March 1957.

Now I know movie versions of novels and plays are sometimes updated to the present time. But I’d never seen a novel updated in such a fashion, and it made me vaguely uncomfortable. Has anyone else seen something similar? Why was it considered necessary, or even desirable?