Look on the publication page, which is one of the first few pages on the left side of the book. The latest date is the date of the edition you are holding in your hands. The book might also list earlier publication dates, including the book's original printing.
Read the forward or introduction. Sometimes editors add introductions to classic books that detail the book's history and cultural significance. Check if they mention any dates.
Locate the ISBN number on the back cover of the book and search it on an online bookseller's website or a university library's online catalog. You can also try the Library of Congress. If you typed the ISBN number in correctly, all publication information registered with the title of the book appears.
Contact a used book dealer. Used book dealers can often determine when a book was published by the appearance of its cover.