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International Sudoku Day

Hobby · September 9

A day for sudoku, the number-placement puzzle played on a nine-by-nine grid, marked in the United States and elsewhere by puzzle fans.

International Sudoku Day falls on Thursday, September 9, 2027. That is 317 days away.

Sudoku is a logic puzzle built on a grid of nine rows and nine columns, divided into nine smaller boxes of three by three. Some squares come filled in. The goal is to fill the rest so that every row, every column and every box holds the digits one through nine exactly once. International Sudoku Day is marked in the United States as well as in other countries.

Despite the numbers, there is no arithmetic involved. The digits could just as easily be letters, colors or shapes. What the puzzle asks for is patience and a habit of elimination: if a seven already sits in this row and that box, it cannot go here, so it must go there. One placed number often unlocks three more, and that small chain reaction is much of the pleasure.

Puzzles range from gentle to fiendish. Easy grids give away many starting numbers, while hard ones offer few and demand longer chains of reasoning. A well-made sudoku has a single solution, so careful logic should always reach it without guessing.

People mark the day the way they solve on any other day, with a pencil, a newspaper page, a puzzle book or an app. Some try a harder level than usual. Others teach a friend the basic rules, which take about a minute to explain and considerably longer to master.

Many solvers write tiny candidate numbers in the corners of empty squares, then erase them one by one. That is why a pencil with a good eraser tends to outlast the pen.

Ways to celebrate

• Solve a sudoku from a newspaper or a free puzzle site.
• Teach a friend or family member the basic rules.
• Try one level harder than you usually play.
• Practice using small pencil notes for candidate numbers.
• Race a friend on the same printed puzzle.

Dates

All national days on September 9

Also on September 9

• National Teddy Bear Day
• National Steak au Poivre Day
• Wiener Schnitzel Day

Categories: Hobby days