Square Root Day was founded by Ron Gordon, a teacher in Redwood City. He keeps this website up about the special day. Gordon suggests it's a good day to get things squared away, or go square dancing.

A numerical pun, Square Root Day celebrates the alignment of a date into the form of the squaring of a number. For example, May 5, 2025, or 5/5/25, represents 5 x 5 = 25, with the square root of ...

This May marks the only time a calendar has a Square Root Day in a 20-year span, with the last one being on April 4, 2016.

Square root days happen only a few times in a century, and the man who brought the day fame is celebrating his sixth one.

A version of this article appears in print on Nov. 23, 2010, Section D, Page 4 of the New York edition with the headline: An Exhibition That Gets to the (Square) Root of Sumerian Math.

Memorising key square roots and using mental math tricks saves time. Techniques like the nearby perfect square trick and weighted averaging enhance problem-solving skills.