The setting of the novel Sense and Sensibility, by Jane Austen, mainly takes place in the English country side. The plot is first set specifically in the county of Sussex, which is located in the South of England.
The Dashwood family's estate of Norland is in the countryside because it was customary of middle class families at that time to favor the simplicity of life in the country versus the flashy and expensive city life in London. However, important parts of the plot do occur in London. Both settings are equally valuable to the story, and just as important.
This being said, the settings of Sussex and London are important because Austen uses these places to illustrate the contrast between city life and country life, and their people. A good example of this is when Mrs. Jennings invites the Dashwood sisters to visit her house in London and, to add to the newness of it all, to a London ball. The sisters' excitement allows the reader to sense the magnitude of the event in the lives of these otherwise simple girls.
The unfortunate treatment that they receive at the ball by the Willoughby set, however, is what opened the Dashwood sisters' eyes to the reality of class distinction. The Dashwoods had to realize the hard way that, as country girls, they would never be welcome in the London circle. This was a good way for Austen to remark the cruelties of high society against those who are not connected to them.
As far as the time period in which the plot takes place, we can see from the time frame in which Sense and Sensibility was published (around 1811-1815) that the novel is set during the Regency period, which took place between 1795-1837. This is the historical time frame of the ruling "Georges" of England. During this period England witnessed many changes in literature and other arts, which may have motivated Austen to indulge in her love of writing. This time period is also considered the "PRE-Victorian" era. This is important because people loosely classify Sense and Sensibility as a Victorian novel. If it were a Victorian novel it would be a very archaic one, since many of the issues present in Sense and Sensibility regarding women were resolved during the Victorian era.
Conclusively, Sense and Sensibility is set during the Georgian/Regency era, around the late 1700's and early 1800's in the Southern countryside of England, specifically in Sussex. The plot also extends to London, where a lot of the rising action takes place, and concludes again in the countryside of Devonshire after the Dashwood sisters got married. Of course, this time they may be accepted in London society- because they married rich men. :)