interesting bit of history but I'm a little confused about the chronology. You start with a letter from Mrs. Figg saying she's going on vacation and can't watch Harry at the Dursleys -- 10 Dec 1986. Then you mention Remus' drunken rage on 26 Jan 1986 which happened when Harry went missing a month (Dec 1985) after Dursleys were arrested and imprisoned. Perhaps Arabella is just completely daft and is watching a non-existent Harry (who went missing 12 months earlier) and mentions Durlseys never taking a vacation because they are, after all, in prison and can't go on holiday (unless you consider prison an extended vacation).
Author's response
I'm assuming you're the same fellow from PS.net, since you're picking up on every detail. I'd like to say a sincere Thank You for your eye to detail. You're the first person to find a bug in the story of merit. As you probably guessed, that's a typo. How it slipped past myself and the betas is a good question, but regardless of how it happened, I went back and fixed Ch9 here at FW and over at SIYE. To save you having to re-read the chapter, there were three edits required, none of which changed the plot a whit. But it's still a terrific catch. Edits: (1) Arabella was gone for "several" not "six" weeks; (2) Arabella was returning about "11 Jan" rather than "23 Jan"; and (3) Remus' drunken rage was "15 Jan 1987", not "26 Jan 1986". I actually check the full moon tables, so when your typo note arrived, I had to see where the Full Moon fell in Jan 1987 and adjust accordingly. Otherwise the first two edits wouldn't have been required. Thanks for the find! It's like that in my detailed story outline and notes, too, which probably explains that the source of the error was a lack of caffeine on my part.