What year was Jem Finch born and how old is he at the end of "To Kill a Mockingbird"? What was the year at the being of the book?

The novel takes place during the 1930s although a specific year is not given. Jem's birthdate is not given either, but the reader can assume that the year he was born in was in the 1920s because chapter one states that Scout was almost six and Jem was nearly ten.

The novel spans a period of three years, so Jem is thirteen at the end of the novel. The first line of the book tells the reader that Jem "was nearly thirteen [when he] got his arm badly broken at the elbow" (Lee). This is referring to the end of the story when Jem and Scout are attacked.