Dewey Decimal System Day December 10th celebrates a system of classification and the man who invented it. On December 10, 1851, Melvil Dewey (1851-1931) was born. The librarian invented the Dewey Decimal system of library classification.

As the most widely used library classification system, the Dewey Decimal Classification (DDC) or Dewey Decimal System has been in use since 1876, the year when American Librarian Melvil Dewey developed and established it. Divided into ten main categories, the numerical system arranges mostly non-fiction publications.

Since its inception, modern libraries maintain the system using modern technologies. A schedule of expansions and revisions helps keep the system current and progressive, too. The DDC is the most widely used classification system in the world. Libraries in 135 countries around the world have translated the DDC into 30 different languages.

It is currently published by the Online Computer Library Center, Inc., and its editorial offices are located within the Decimal Classification Division of the Library of Congress.

Melvil Dewey

Dewey’s interest in simplification led him to create a system that revolutionized library science. Born Melville Louis Kosuth Dewey in update New York, he was only 21 when he invented the Dewey Decimal Classification system.

He also established library standards and advanced library education. Dewey went on to help develop the American Library Association and founded and edited the Library Journal. As an entrepreneur, he sold library supplies. Dewey paved the way for new librarians by establishing the first library school at Columbia College in New York City and later became the director of the New York State Library in Albany.

HOW TO OBSERVE #DeweyDecimalSystemDay

Visit a library and explore using the Dewey Decimal System.

  • Read about library organization or take a tour of your local library to learn more about the technology it uses.
  • Learn about library sciences.
  • Read a book about Melvil Dewey such as The Efficient, Inventive (Often Annoying) Melvil Dewey by Alexis O’Neill and illustrated by Edwin Fotheringham.
  • Discover different professions in a library degree program. The Dewey Decimal System is one tool librarians use. There are so many more!

Use #DeweyDecimalSystemDay to post on social media.


While the observance commemorates the anniversary of Melvil Dewey’s birth, National Day Calendar® continues searching for the introduction of the first celebration. 

Dewey Decimal FAQ

Q. Where does science fiction fall in the Dewey Decimal Classification (DDC)?
A. There are 10 broad classifications in the DDC. Science fiction as well as other works of literature fall under the 800-899 Literature classification.

Q. I’m writing my memoirs. How will the DDC classify my book?
A. Memoirs are usually found under 900-999 History and Geography classification.

Q. Is there another classification system used?
A. Yes. Many libraries use the Library of Congress Classification System (LC).