A book I read recently takes place in 1923. The full moon that occurs in December is a significant plot point.
Is there a listing of the dates of full moons that the author may have consulted, or did the author just say “Hey, this works for me. Who’s gonna know otherwise?”
Oh, lots. It’s easy with computers now.
Or if you’d rather a contemporary source: 1923PASP...35..250M Page 250
(The numbers are a bit different due to geography; the first link is in Central European time, the second in Pacific time.)
Y’know, I just realized that getting an answer to that question 30 years ago would have taken you the better part of an afternoon. You’d have to get in the car and drive to the library, ask the librarian your question, find the right microfilm, put it in the machine and scan with your own eyeballs to find the answer… And that, boys and girls, was the world before Google.
Not necessarily. All you’d actually need would be some source that give the synodic period of the Moon to enough precision, the date of any one full moon, and a little willingness to do the math.
Thank you all. It seems the author got it right.
Okay, who else thought ‘werewolf cosplay’?
Nope, the book is titled Bride of the Rat God.
Going looking for a link to it I found this, Wow!
You could also use this little gem of an internet resource called Wolfram Alpha:
Let’s say I want to know when there was a full moon in Utica, NY in December 1923. I go to the Wolfram Alpha website and type in this search query:
full moon december 1923 utica, ny
which gives me this result:
I wouldn’t even have known where to start if I had wanted to do this type of research 20 years ago.
As Chronos notes, it’s actually a small amount of research coupled with some not-very-formidable math.
But 20 years ago, you had to have a well above average knowledge of - or interest in - astronomy. And in addition to that, you probably needed access to a good library.
Today, even with a passing interest in the subject, I get that information in 10 seconds, never leaving my chair.
I hear Pluto is now single … 
All the girls are into vampires and werewolves now, so it should be a piece of cake.
An old almanac, say. Or a (pocket) calendar showing when Easter fell and knowledge of its link to the full moon would give you the year’s full moons with an occasional deviation of one day: this would not require an extraordinary knowledge of astronomy, just an amount of religious education which many of my older relatives have.
True, haven’t thought of that.
But given the OPs question, how many people would have grabbed a perpetual calendar and done the calculation just to verify if the author of the book got it right?
The Internet makes it so much easier.
You know, when I read the title I actually thought for a second, “Why does the op only want to find a social for the night of a full moon?”
No. You needed a World Almanac, a book which would have been on the shelf of any self-respecting pre-Internet writer.
A one-minute browse through the World Almanac would give you the only two pieces of information you need: (1) A full moon will occur on December 28, 2012; and (2) the moon’s synodic period is 29.530589 days.
To offset back to 1923, we go back (365.25*89) = 32,507.25 days, rounding up to 32,508 because this year is a leap year. Then we divide 32,508 / 29.530589 = just under 1,101 lunations. Take 1,101 * 29.530589 = 32,513 and a butt days. That’s five days more than 89 years, so we offset back five days to a full moon on December 23, 1923.
See how easy? No afternoon in the library required.
(Granted, it would be a little harder and more error-prone, pre-calculator.)
Am I the only one who thought about eHarmony when reading the thread title?
True. But I would argue that even this type of reasoning is beyond the scope of your average fiction writer with a degree in English who has been out of school for some time.
Right, but first I’d have to find someone like you who know how to set up the calculation!
Try a Catholic priest.