I am trying to use AJAX with Drupal 6. How do I determine the URL I am trying to contact? I looked at the documentation here and it left me a bit confused. I don't need to access any files, I am just returning the date that is on the server to my Javascript code. (I don't want the date/time from the user's perspective) 

The example gives this in the javascript portion of the example. This example seems to already know where get should call to get the response back. I am not sure what the URL would be on my server to just talk to my php code.

$.get('/photos/get/photos/' + parseInt(this.id, 10), null, imageDetails);
        return false;
The URL you use is the one that delivers you the data you want.  If you want to grab the server time you can create a short PHP script that gets the info and then make that info available to JS using Drupal.settings.

For example:

// Create the array that is required by drupal_add_js()
$server_time = array(
  'serverTime' =&gt; date("h:i:sa"),
);

// This is what makes the variable available to JS
drupal_add_js(array('time' =&gt; $server_time), 'setting');


Then, in your.js:

var time = Drupal.settings.time.serverTime;