NURE Kharkiv national university of radioelectronics

Department of Applied Mathematics

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Square Root Day

May 5, 2025 is Square Root Day.

Square Root Day is an unofficial holiday celebrated on the day when the day of the month and the number of the month are the same and equal the square root of the last two digits of the current year. In each century, there are only 9 such dates.

In the 21st century, Square Root Day has already been celebrated on:

  • January 1, 2001 (01/01/01);
  • February 2, 2004 (02/02/04);
  • March 3, 2009 (03/03/09);
  • April 4, 2016 (04/04/16).

The upcoming dates for this holiday will be:

  • June 6, 2036 (06/06/36);
  • July 7, 2049 (07/07/49);
  • August 8, 2064 (08/08/64);
  • September 9, 2081 (09/09/81).

The dates of Square Root Day in any century are always the same because only the last two digits of the year are used to determine the date of the holiday. For mathematical reasons, the holiday never falls on any days between October and December.

For the first time (and the only time in the 20th century), Square Root Day was celebrated on September 9, 1981 (09/09/81). The founder of this holiday is considered to be Ron Gordon, a high school teacher from Redwood City, California, USA. Enthusiasts of the holiday suggest serving root vegetables cut into cubes (symbolizing square roots) or baked goods shaped like square root symbols on this day.

In 2004, Square Root Day coincided with Groundhog Day (February 2, 2004), and in 2016 with Internet Day (April 4, 2016). The date January 1, 2001, coincided with the beginning of the 21st century and the 3rd millennium. In 2009, in honor of Square Root Day (March 3, 2009), Ron Gordon held a contest with a prize pool of $339.

It is worth noting that the 2025 Square Root Day was special, as not only were the last two digits of the year a square (25 = 5²), but the entire year itself was a perfect square (2025 = 45²). The previous “square” year was 1936 (1936 = 44²), though Square Root Day was not celebrated back then, and the next such year will be 2116 (2116 = 46²).

Although Square Root Day is not widely recognized, it showcases the beauty of mathematics, drawing attention to interesting numerical facts and their presence in everyday life. In line with Sustainable Development Goal 4: Quality Education, this expands opportunities for promoting education in mathematics and the natural sciences.

The official website of this holiday is https://squarerootday.net.