# Question about finding dates for full moons. **URL:** \ **Category:** Factual Questions\ **Created:** [April 23, 2012, 3:47am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662 "2012-04-23T03:47:52Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Baker](https://avatars.discourse-cdn.com/v4/letter/b/bb73d2/32.png) [@Baker](https://boards.straightdope.com/u/Baker)\ **Post date:** [April 23, 2012, 3:47am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/1 "2012-04-23T03:47:52Z")
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?” ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [April 23, 2012, 3:52am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/2 "2012-04-23T03:52:09Z")
Oh, lots. It’s easy with computers now. > **[Full moon calendar 2023](https://www.fullmoon.info/en/fullmoon-calendar/1923.html)** > > The full moon calendar 2023 with exact dates and time accurate to the second. Or if you’d rather a contemporary source: [1923PASP...35..250M Page 250](http://adsabs.harvard.edu/full/1923PASP...35..250M) (The numbers are a bit different due to geography; the first link is in Central European time, the second in Pacific time.) ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [April 23, 2012, 3:54am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/3 "2012-04-23T03:54:54Z")
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. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 23, 2012, 4:02am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/4 "2012-04-23T04:02:51Z")
> [@](#): > > 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. ---
**Author:** ![Baker](https://avatars.discourse-cdn.com/v4/letter/b/bb73d2/32.png) [@Baker](https://boards.straightdope.com/u/Baker)\ **Post date:** [April 23, 2012, 4:21am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/5 "2012-04-23T04:21:46Z")
Thank you all. It seems the author got it right. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [April 23, 2012, 4:30am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/6 "2012-04-23T04:30:19Z")
Okay, who else thought ‘werewolf cosplay’? ---
**Author:** ![Baker](https://avatars.discourse-cdn.com/v4/letter/b/bb73d2/32.png) [@Baker](https://boards.straightdope.com/u/Baker)\ **Post date:** [April 23, 2012, 4:41am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/7 "2012-04-23T04:41:42Z")
Nope, the book is titled Bride of the Rat God. Going looking for a link to it I found this, Wow! > **[Eve--The Bride Of The Rat God.](https://boards.straightdope.com/sdmb/showthread.php?t=256146)** > > I’ve owned this book for several years, & throughly enjoy it. I noticed one of your posts on the movies, & thought of you. LINK to :“Bride Of The Rat God” Barabra Hambly has done a number of horror/dark fantasy books, but this one is set... ---
**Author:** ![Donnerwetter](https://avatars.discourse-cdn.com/v4/letter/d/b2d939/32.png) [@Donnerwetter](https://boards.straightdope.com/u/Donnerwetter)\ **Post date:** [April 23, 2012, 10:31am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/8 "2012-04-23T10:31:05Z")
You could also use this little gem of an internet resource called Wolfram Alpha: > **[Wolfram|Alpha: Making the world’s knowledge computable](https://www.wolframalpha.com/)** > > Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels. 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: > **[full moon december 1923 utica, ny - Wolfram|Alpha](https://www.wolframalpha.com/input/?i=full%2Bmoon%2Bdecember%2B1923%2Butica%2C%2Bny)** > > Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels. I wouldn’t even have known where to start if I had wanted to do this type of research 20 years ago. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [April 23, 2012, 1:20pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/9 "2012-04-23T13:20:20Z")
> [@Donnerwetter](#): > > 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. ---
**Author:** ![Donnerwetter](https://avatars.discourse-cdn.com/v4/letter/d/b2d939/32.png) [@Donnerwetter](https://boards.straightdope.com/u/Donnerwetter)\ **Post date:** [April 23, 2012, 1:56pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/10 "2012-04-23T13:56:50Z")
> [@Chronos](#): > > 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. 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. ---
**Author:** ![Malthus](https://avatars.discourse-cdn.com/v4/letter/m/85f322/32.png) [@Malthus](https://boards.straightdope.com/u/Malthus)\ **Post date:** [April 23, 2012, 2:01pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/11 "2012-04-23T14:01:03Z")
I hear Pluto is now single … 😃 ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 23, 2012, 2:15pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/12 "2012-04-23T14:15:05Z")
All the girls are into vampires and werewolves now, so it should be a piece of cake. ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [April 23, 2012, 2:16pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/13 "2012-04-23T14:16:51Z")
> [@Chronos](#): > > 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. 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. ---
**Author:** ![Donnerwetter](https://avatars.discourse-cdn.com/v4/letter/d/b2d939/32.png) [@Donnerwetter](https://boards.straightdope.com/u/Donnerwetter)\ **Post date:** [April 23, 2012, 2:36pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/14 "2012-04-23T14:36:15Z")
> [@Nava](#): > > 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. ---
**Author:** ![BubbaDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bubbadog/32/333_2.png) [@BubbaDog](https://boards.straightdope.com/u/BubbaDog)\ **Post date:** [April 23, 2012, 2:45pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/15 "2012-04-23T14:45:36Z")
> [@Malthus](#): > > I hear Pluto is now single … 😃 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?” ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [April 23, 2012, 2:51pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/16 "2012-04-23T14:51:32Z")
> [@Donnerwetter](#): > > 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. 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.) ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [April 23, 2012, 3:03pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/17 "2012-04-23T15:03:17Z")
Am I the only one who thought about eHarmony when reading the thread title? ---
**Author:** ![Donnerwetter](https://avatars.discourse-cdn.com/v4/letter/d/b2d939/32.png) [@Donnerwetter](https://boards.straightdope.com/u/Donnerwetter)\ **Post date:** [April 23, 2012, 3:27pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/18 "2012-04-23T15:27:51Z")
> [@Freddy\_the\_Pig](#): > > 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.) 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. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [April 23, 2012, 5:53pm UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/19 "2012-04-23T17:53:13Z")
> [@Freddy\_the\_Pig](#): > > 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.) Right, but first I’d have to find someone like you who know how to set up the calculation! ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [April 24, 2012, 7:24am UTC](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662/20 "2012-04-24T07:24:48Z")
> [@WhyNot](#): > > Right, but first I’d have to find someone like you who know how to set up the calculation! Try a Catholic priest. [Next page](https://boards.straightdope.com/t/question-about-finding-dates-for-full-moons/619662.md?page=2)