Square Root Day

Square Root Day is an unofficial holiday celebrated on days when both the day of the month and the month are the square root of the last two digits of the year. There are nine square root days that always fall on the same dates each century.There is an exception to this rule, where during this millennium there will be three extra square root days that fall on 10-10-2100, 11-11-2121, and 12-12-2144. Otherwise the dates for each century fall on 01-01-01, 02-02-04, 03-03-09, 04-04-16, 05-05-25, 06-06-36, 07-07-49, 08-08-64, and 09-09-81.

Ron Gordon, a high school teacher from Redwood City, California, created the first Square Root Day for September 9, 1981 (09-09-81). He remains the holiday’s publicist, sending news releases to world media outlets. His daughter set up a Facebook group for people to share how they celebrate the day. One suggested way of celebrating the holiday is to cut up root vegetables into squares, thus making a “square root”.

The number of years between consecutive Square Root Days in a century are consecutive odd numbered years: 3, 5, 7, 9, 11, 13, 15, 17. This demonstrates the fact that every odd number is the difference of two consecutive squares.