How do themes differ from periods as tools for understanding history?

Themes explored in various pieces of literature usually reflect the spirit of the age in which they were made. The spirit of the age is usually a historical thing that is based on the previous periods and the history that created it. An example of this is the ideas of modernism that came in response to World War 1 where people were depressed and obsessed with the bad things in the world.

They most like influence us and there self