title: Jquery Dropdown Date Validation
body: <p>I am using the jQuery Validation plugin to validate a signup form for my site.  One of the required things a user must do is enter their birthday, they have to be 18 to use the site.  I am having the birthday entered through three dropdown menus.  I want to validate this entry (to make sure they did it and to make sure they are at least 18, but I am failing to understand the building of custom validators.  Here is my code in the form:</p>
  
  <pre><code>&lt;p&gt;
              &lt;label for="user_birthday"&gt;Birthday&lt;/label&gt;
              &lt;br&gt;
              &lt;select id="user_birthday_2i" name="user[birthday(2i)]"&gt;
              &lt;option value="1"&gt;January&lt;/option&gt;
              &lt;option value="2"&gt;February&lt;/option&gt;
              &lt;option value="3"&gt;March&lt;/option&gt;
              etc....
              &lt;/select&gt;
              &lt;select id="user_birthday_3i" name="user[birthday(3i)]"&gt;
              &lt;option value="1"&gt;1&lt;/option&gt;
              &lt;option value="2"&gt;2&lt;/option&gt;
              &lt;option value="3"&gt;3&lt;/option&gt;
              etc...
              &lt;/select&gt;
              &lt;select id="user_birthday_1i" name="user[birthday(1i)]"&gt;
              &lt;option value="2010"&gt;2010&lt;/option&gt;
              &lt;option value="2011"&gt;2011&lt;/option&gt;
              etc...
              &lt;/select&gt;
            &lt;/p&gt;
  </code></pre>
  
  <p>Anyone ever built a validator like this before using the jQuery Validation plugin?</p>