The opening lines of Persuasion reflect several precise dates:
“‘Walter Elliot, born March 1, 1760, married, July 15, 1784, Elizabeth, daughter of James Stevenson, Esq. of South Park, in the county of Gloucester, by which lady (who died 1800) he has issue Elizabeth, born June 1, 1785; Anne, born August 9, 1787; a still-born son, November 5, 1789; Mary, born November 20, 1791.’
Precisely such had the paragraph originally stood from the printer’s hands; but Sir Walter had improved it by adding, for the information of himself and his family, these words, after the date of Mary’s birth–‘Married, December 16, 1810, Charles, son and heir of Charles Musgrove, Esq. of Uppercross, in the county of Somerset,’ and by inserting most accurately the day of the month on which he had lost his wife.”
Northanger Abbey’s opening gives no hints as to the date when the story is set, while Mansfield Park opens with “about thirty years ago.” Thus, there seems to be a clear progression in Austen’s concern for the setting as she grows more detailed as her writing develops. I think an important question to ask here is whether or not explicit details (like the exact dates she provides in the passage above) is an improvement in her writing, or whether the middle-ground of Mansfield Park (a ball-park date) or the completely ambiguous Northanger Abbey is the most effective.
Personally, I think the ambiguity suits Northanger Abbey specifically because of its tendencies toward the Gothic, and Gothic novels tend to be set in the obscure past. But, as for her purely Romantic works, I prefer not knowing the exact details, yet the progression in her novels seems to show that Austen saw this exactness as an improvement. Why do you think that is? Do these exact dates somehow make the story feel more real, more rooted to the audience’s reality?