To Square or Not To Square
National Square (Root) Day may not be new. I didn't bother to check, but I've never heard of it before.
It certainly could have been celebrated on 4/4/04, 4/9/04, 4/16/04, and so on.
Seeing as how you can either consider this National Square Day or National Square Root Day, there are many ways to commemorate it.
For one, anytime you see a square number, such as 4, 9, 16, 25, etc., you should use its square root (2, 3, 4, 5...) instead.
Going the other direction, anytime you see a number - 3, 14, 73, 12,765 - you should use its square - 9, 196...whatever - instead.
There is another possibility for celebration here, if you consider this National Square Day. You can go geometric instead of algebraic. Look for four-sided figures with right angles and sides of equal length.
What you do when you find one (and you will) is left to your imagination.