(marekuliasz/iStockphoto | Getty Images)Once a century, a very special day comes along. Pi Day (3/14) often comes with sweet treats; Square Root Day (4/4/16 or 5/5/25, for example) has a certain numerical rhyme. Celebrate Square Root Day today! Here’s how to celebrate the rare date The rare palindrome date also coincides with National Margarita Day in the U.S. In any case, Adams says that if it were up to him, he’d call the day Pythagorean Triple Square Day.