National Day

Dewey Decimal System Day

Celebrated on 12/10/2026

Quick Fact

Did you know that the Dewey Decimal System, created by Melvil Dewey in 1876, is used in over 200,000 libraries across 135 countries? Despite its age, it remains one of the most widely adopted library classification systems, with updates still being made to its 21st major edition.

Origins and Establishment of Dewey Decimal System Day

Dewey Decimal System Day is celebrated annually on December 10th, the birthday of Melvil Dewey (1851–1931), who invented the Dewey Decimal Classification (DDC) system in 1876 while working as a librarian at Amherst College. The day was established by librarians and library advocates to honor Dewey's contribution to organizing knowledge. The first known celebration was in 1951, the 100th anniversary of Dewey's birth, promoted by the American Library Association (ALA), which Dewey co-founded.

Evolution and Modern Commemoration

Over time, Dewey Decimal System Day has evolved from a niche observance among catalogers to a broader celebration in libraries and schools. Modern commemorations include library tours explaining the DDC, interactive games teaching classification, and social media campaigns using #DeweyDecimalDay. Some libraries host "re-shelving races" or create displays highlighting books from different Dewey classes. Since the DDC is now owned by OCLC (Online Computer Library Center), they often release special resources or updates on this day.

Facts & General Observations

  • The Dewey Decimal System has been translated into over 30 languages and is used in more than 200,000 libraries worldwide.
  • The system is revised approximately every 7 years; the latest print edition (Volume 23) was published in 2011, with continuous updates via WebDewey.
  • Melvil Dewey was also a founder of the American Library Association and the first library school at Columbia University, making him a pivotal figure in modern librarianship.

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