International Sudoku Day Date in the current year: September 9, 2024

Sudoku is a logic-based puzzle where you have to fill a 9x9 grid with digits so that each row, column and 3x3 subgrid contain all digits from 1 to 9. It is based on magic squares (squares filled with numbers whose sums are the same in each column, each row, and both main diagonals). The Sudoku puzzle comes with a partially completed grid; a well-thought-out Sudoku has only one solution.

Despite its Japanese name, Sudoku – or, to be more precise, its predecessors – actually originated in France. In the late 19th century, French puzzle setters began to experiment with grid-based number puzzles by removing numbers from magic squares. The first such puzzle was published in an 1892 issue of Le Siècle, a Paris daily newspaper. It shared key characteristics with the modern Sudoku, such as a 9x9 grid consisting of 3x3 subgrids; however, unlike the modern Sudoku, it contained double-digit numbers.

Three years later, La France – the main rival of Le Siècle – published the refined version of the puzzle named “diabolical magic square” (carré magique diabolique). The only difference between La France’s puzzle and the modern Sudoku was that the former did not have 3x3 subgrids.

Magic square-based number puzzles remained a regular fixture in French newspapers until about the time of the First World War. They were reinvented in the United States in the late 1970s. The person credited with inventing the modern Sudoku is Howard Garns, an architect from Indiana, whose puzzle named Number Place was published anonymously in a 1979 issue of Dell Pencil Puzzles and Word Games.

Maki Kaji, the president of Japanese puzzle publisher Nikoli, got interested in the puzzle and introduced it in Japan. Originally named Sūji wa dokushin ni kagiru (“the digits must be single”), the name of the puzzle was shortened to Sudoku for convenience.

In 2004, Hong Kong judge Wayne Gould created a computer program that could generate unique Sudoku puzzles. He brought his puzzles to Britain, where it is traditional for newspapers to publish crosswords and other puzzles, and convinced The Times to publish them. Shortly after, a Sudoku puzzle by Wayne Gould was published by The Conway Daily Sun in the United States.

Since then, Sudoku puzzles have spread throughout the world and become popular among puzzle enthusiasts. International Sudoku Day was created in 2013 by the World Puzzle Federation, a global federation of national organizations with an interest in puzzles. The date of the holiday, September 9 (9/9), was chosen to represent the 9x9 grid of the classic Sudoku puzzle.

You can celebrate International Sudoku Day by participating in an in-person Sudoku tournament near you, signing up for an online tournament, challenging a friend to play Sudoku head-to-head, or simply solving Sudoku puzzles at your own pace. And don’t forget to spread the word on social media with the hashtag #InternationalSudokuDay.