title: How can I have my DateTimeField filled in automatically for my admin entries?
body: <p>I have a <code>date_added</code> field for my entries and it's frustrating clicking the date and time when filling these in. I want this to happen behind the scenes and I don't want these to even show up.</p>
  
  <p>I've googled around and tried searching SO but was unable to find a snippet of how this can be done when I save my form.</p>
  
  <p>Here's the relevant bit from <code>admin.py</code>:</p>
  
  <pre><code>class BugForm( forms.ModelForm ):
      class Media:
      #js = ( 'http://static.arounds.org/wmd/wmd.js', )
      js = ( 'http://ajax.googleapis.com/ajax/libs/mootools/1.2.3/mootools-yui-compressed.js', 'http://static.arounds.org/js/moowmd.js', 'http://static.arounds.org/js/wmd-config.js' )
      css = {
          'all': ('http://static.arounds.org/css/wmd.css',)
      }
  
      class Meta:
      model = Bug
  
  class BugAdmin( admin.ModelAdmin ):
      fields = ['name', 'slug', 'excerpt', 'summary', 'date_added', 'poster', 'categories', 'status']
      prepopulated_fields = { 'slug' : ['name'] }
      form = BugForm
  </code></pre>
  
  <p>I'm aware that I'll have to probably specify <code>exclude = ('date_added',)</code> and define a <code>def save()</code> function, but I'm not sure of the specifics needed for this.</p>