The time-frame was from after the civil-war until the 1920's or 30's, and this was a time where a lot of old cities in the south were reeling from the after-effects of war and the abolition of slavery. What used to be wealthy, upper-class families with a lot of money were left without anything but the legacy of their name. Because of the notoriety of being from a wealthy southern family, these people (the Griersons in the story) were like the Hollywood celebrities of the time; we love to watch them, analzye their lives, and gloat a bit in their downfalls. This celebrity gossip is what allows the narrator to represent the townsfolk as a whole, and what allows us to get such a complete picture, considering we never really go beyond the townspeople's perspectives.
As time goes on, the townspeople forget, eventually about Emily, until the scandalous news of the surprising discovery comes about. She is no more than a curiosity to people; they go to her house like it is a viewing of an ancient museum, which emphasizes how times have really changed, and how people like Emily Grierson, with all of her elite background, have become obsolete. From the beginning with her father in a more relevant and prominent position, to the end where Emily is no more than a museum relic, the story covers the deterioration and disappearance of a certain era in Southern history.
Faulkener was a master at manipulating time. One can see this in some of his other stories and novel, especially "As I Lay Dying" and "The Bear", among others. As for "A Rose for Emily", Faulkner does not tell the story in simple chronological order. He weaves the story in and out of various time periods. Through the perspective of the narrator, he forces the reader to piece together events from a series of seemingly random observations of a townsperson. For example. the story opens with Emily's death and funeral and then digresses to her battle over taxes after her father died. The story then jumps to two years earlier and we learn the details of her father's death and " a short time after he sweetheart...had deserted her." We learn first about the smell around her house and then her father's death, which came before the smell. The story then jumps to her relationship with Homer Barron and her request for poison. The reader is forced to put all of this together to discover the fact that Emily had poisoned Homer with the poison and the smell was that of Homer's decaying body. We are finally brought back to Emily's funeral and the quick departure of her Negro servant. But that is not the end of the story. Faulkner waits until the very last line to tell us the real horror surrounding Miss Emily when chronologically most of it had occurred sometime earlier. But time is not as important to Faulkner as the impact of the story. So, he saves that for the end.