Square Root Day is any day "where the day and the month are both the square root of the last two digits in the current year." 3/3/09 is one of only 9 such days in the century. The next one will be 4/4/16.
Eat a square root to celebrate -maybe cut your potato into little square pieces today.
The picture at the top of the page is from a resource site for the Florida school system.