This webpage about Basic Arithmetic Dates (BADs) was created on 17 September 2009 even though the first BAD was posted on 1 March 2006. The webpage was created because I was tweeting BADs to the @mathbabbler Twitter account.

Basic Arithmetic Date (BAD) is a math equation that is "found" using the numbers in a MM/DD/YY formatted date. The goal of BADs is to help turn us into `equationeers` (i.e. finders of equations).

Every number in the date must be used and each number can be used only once. Equations are constructed using the add, subtract, multiply, divide, modulo and exponent operators.

```   24 August 2003   :  08/24/03... 24 / 3 = 8
22 September 2004:  09/22/04... 22 % 9 = 4
12 July 2005     :  07/12/05... 12 - 7 = 5
02 April 2008    :  04/02/08... 4 * 2 = 8
03 February 2009 :  02/03/09... 3^2 = 9
04 May 2009      :  05/04/09... 5 + 4 = 9
```

Math functions such as `sqrt(n)`, `cuberoot(n)`, `log(n)`, `factorial(n)`, `summation(n,m)` `floor(n)`, `ceil(n)` and `avg(n,m)` can be used.

```   03 January 2006  :  01/03/06... summation(1,3) = 6
07 August 2008   :  08/07/08... 8! / 7! = 8
18 August 2009   :  08/18/09... cuberoot(8) * 9 = 18
21 September 2009:  09/21/09... 21 % 9 = sqrt(9)
08 July 2009     :  07/08/09... avg(7, 9) = 8
10 September 2009:  09/10/09... 9 * log(10) = 9
```

Math equations can be constructed that evaluate to the mathematical constants Pi (rounded to nearest hundredth) and Phi.

```   02 January  2005:  01/02/05... (1+sqrt(5))/2 = Phi
22 February 2005:  02/22/05... 22/(2+7) = Pi
```

By default numbers are expressed in base-10; however, base-MM, base-DD, and base-YY can be used on any of the numbers.

```   17 September 2009:  09/17/09... sqrt(9)^(sqrt(sqrt(179))) = 9
12 May       2009:  05/12/09... (5!/12)9 = 9
```

Common logarithms (base-10) are allowed without having a 10. Logarithms in other bases are restricted to the numbers comprising the date.

```   22 September 2009:  09/22/09... 22/(log[9,9]+sqrt(9)!) = Pi
```
12 May 2009: 05/12/09... (5! / 12)9 = 9