4/4/16 is **Square Root Day**! Square Root Days occur when the month (4) and the day (4) are both equal to the **square root** of the year (16).

The *square* of a number is the product of the number times itself. The number that is multiplied by itself is called the *square root* of the product! In our example above, 4 is the square root of 16, because 4 x 4 = 16. The square root of a number can be written using the radical symbol, √, which, in our opinion, looks pretty darn radical:

√ 16 = 4

Square Root Days are rare and special—*there are only nine Square Root Days per century*!

- 1/1/01
- 2/2/04
- 3/3/09
- 4/4/16 →
*Today!*
- 5/5/25 →
*The next Square Root Day! Mark your calendars!*
- 6/6/36
- 7/7/49
- 8/8/64
- 9/9/81

**More fun facts about square roots:**

When you multiply a whole number by itself, the product is called a *perfect square*! In our example, 16 is a perfect square because it’s the product of 4 times itself.

All perfect squares end in the digits 0, 1, 4, 5, 6, & 9. Check out the years in our list of Square Root Days above—they all end with one of these digits, which means they are perfect squares!

The square roots of all numbers which are *not* perfect squares are *irrational numbers—*numbers whose decimal representations never end nor exhibit consistent repeating patterns. (P.S. Here’s a math holiday throwback for you: The most popular irrational number is Π!)

**So how exactly does one celebrate Square Root Day?** Per Wikipedia, you could eat root vegetables cut into shapes with square cross-sections, thereby indulging in literal “square roots.” If this doesn’t sound particularly delectable or festive, consider enjoying a square piece of carrot cake—carrots are roots, after all!

You could also…

Can you think of your own fun and creative ways to celebrate Square Root Day?