Wherever there's adventure to be found.....

[Zar Quon]

If I remember rightly,they decided to set it in one year from the period -off the top of my head I think it was 1953, for continuity throughout the series.Someone here may remember the details better than me??

I think they did the same thing with Poirot (David Suchet) and Miss Marple-again I think they picked a date in the 1950's for period continuity.(again 1953 seems to come to mind again!)
I'm sure there are some here who may remember more about that?/

Suchet's Poirot really should moved forward from pre-war tho given that the source material is (IIRC) almost always contempory to the published date (I stand to be corrected on that tho). Not really watched most of the modern Marples, but they seem to be a vaguely mid-'50s setting. I think the Joan Hickson Miss Marples moved forward a year or two every couple of adventures/cases tho.....

[Moonraker]

Agatha Christie wrote Curtain, Poirot's final case in which he revealed the criminal posthumously, during the second world war. However, her publishers persuaded her to keep it back, as they could see much more mileage in in our Belgian friend. It was therefore moved forward by a few decades! I think the setting is ideal, and would not want to see it moved too far ahead. The stories did, however, move into the sixties (Third Girl, for example), so I can't see much wrong with the chronology. Even in keeping to these time restraints, it must be noted that Hercule would have been about 120 when he finally died!

[Jamie]

I thought it was smeg-awful, not least because it contained the 1990's script revisions but was clearly set in the 50's. (Not even the right decade, as it should have been the 40's.)

Nine titles were published in the 50s, so not sure why you consider it not to be the "right decade"!

I was being kinda tongue in cheek, but if y'all want to get all serious...

Date of publication does not necessarily correspond to the date of the setting. Blyton clearly intended for her works to be contemporary, so Julian would have been twelve, Dick and George Eleven and Anne ten in 1942. By the time the series was finished being published Julian would have been well into his twenties if the date of publication had corresponded to the setting of the story, yet it's clear that none of the kids ever hit serious puberty, despite the number of summer holidays they somehow manage to pack into eighteen months or two years.

[Jamie]

I thought it was smeg-awful, not least because it contained the 1990's script revisions but was clearly set in the 50's. (Not even the right decade, as it should have been the 40's.)

Nine titles were published in the 50s, so not sure why you consider it not to be the "right decade"!

& then there's the last 4 published in the early '60s

If I could refer the smiley brigade to the answer I gave some moments ago.