The setting of a novel includes not simply where the story takes place, location, but also the time and the time period wherein the change of events occurs.
Time and time period, like setting are important dimensions to a story. In many stories they act as additional characters.
If the time period is not the present, this also includes reading about what was taking place during the time period of the novel.
For all novels, even those situated in the present, establishment of setting requires writing down a time line of birth dates for characters, and important events in the lives of those characters, such as when they graduated college, married, gave birth.
We want to also take note of the dates and times of emotional upheavals.
Say for instance a protagonist underwent major surgery wherein she or he almost died. The author wants to know what year or where along the continuum of various relationships that appear in the novel this event took place.
Writers need not present these time lines to readers in a didactic way, although some novels are crafted in such a manner that requires a family tree to be listed at the front of the book.
Whether you do this or not is the author’s decision. In any case the author needs to have a clear understanding of these dates concerning major characters and how the events in the characters’ live effect the present set of happenings addressed in the novel.
Time is a major dimension of plot. Thus the aspect of time serves as a transporter of both character and plot, which flows out of character. Another way of looking at this is that time, past and present suffuses personality with texture.
As with plot, research for a novel is both external and didactic as well as internal and emotional. Both contribute to the development of a full and rich narrative line that encompasses whole world of the protagonist and her or his supporting characters.