Display of comment_date within get_comments?

The way you’re doing this, you’re going to get the raw SQL date that’s stored in the wp_comments table.

You can still use the convenience functions like comment_date with get_comments. In this case, we’ll use get_comment_date. The first argument is the date format — if you leave it blank, WP will use whatever date format is set in the options > general page.

<?php
foreach($comments as $comment) :
   echo "<li class=clearfix>
   <span class=comment-details>{$comment->comment_content}</span>";
   echo '<span class=comment-date>' . get_comment_date( '', $comment ) . '</span>';
   echo "<span class=comment-author>By {$comment->comment_author}</span>

   </li>";
endforeach;

Otherwise you could use PHP’s strtotime and date to generate the date format you want.

date('F j, Y', strtotime($comment->comment_date));