How to use ungrouped date fields as data for Charts Views?
I found a partial workaround for this by using hook_views_pre_render.

function hook_views_pre_render(&amp;$view) {
   if($view-&gt;name == 'stuff'){
      $results = &amp;$view-&gt;result;
      foreach ($results as $key =&gt; $result) {
      $now = time();
      $end = strtotime($result-&gt;field_field__end_date_[0]['raw']['value']);
      $daysuntil = date("j", $end-$now);
      $result-&gt;field_field_end_date[0]['rendered']['#markup'] = $daysuntil;
     }
   }
}


The previous function is  for a chart that displays node serials as x-axis labels and number of days for yaxis, which is calculated as the difference  between now and a end date.