Did you know that today, April 4, 2016, is the fourth Square Root Day of the century?

What is Square Root Day?

Square Root Day is an unofficial holiday celebrated on days when both the day of the month, and the month itself, are the square root of the last two digits of the year.

Founded by American high school teacher, Ron Gordon, the first Square Root day was celebrated on September 9, 1981.

There are only nine Square Root Days in a century, with the final Square Root Day of the century falling on September 9, 2081.