As I said, I wanted my story to be easily relatable to contemporary readers.
A girl in 1812 inhabited a vastly different world technically and, as a result, culturally from a girl in 2012: No cars, no airplanes, no supermarkets, no electricity, no TV, no Internet, no telephones, no flush toilets.
But a girl on 1912 lives in a far more familiar culture: Cars and planes (albeit primitive), electricity in most homes (ditto plumbing). TV is still just a gleam in Philo Farnsworth's eyes, but there are movies. Radio is just beginning, but newspapers are linked by wire services. No computers, but adding machines and typewriters exist so number pads and keyboards are everywhere.
And there are telephones.
Split the difference -- 1962 -- and not that much changes. TV and radio, to be sure, but no Internet yet. Still, most of the changes are in style and degrees; the world of 1962 is easily understandable to a reader in 2012.
Problem: You can't lose a bunch of school kids in 1962, either.
Split the difference again -- 1937 -- and suddenly the solution presents itself. World War Two, at least the Pacific portion of it, started December 7th, 1941.
Now we have a logical reason why no one comes looking for the girls: All hell is breaking loose, and the loss of a handful of girls is just one more tragic drop in a bucket brimming with tears.
Problem: Every island worth fighting over was fought over.
This is why Google was invented. A quick search revealed that every island capable of hosting a permanent human settlement had a permanent human settlement.
But what exactly constitutes a "permanent" settlement?
(to be continued)