Your code is correct, however is $pilotinfo the correct variable? You will see 1969 if it returns 0 or null.
When in profile_main.tpl you will want to use $userinfo, like so:
<li><strong>Date Joined: </strong><?php echo date(DATE_FORMAT, strtotime($userinfo->joindate));?></li>
<li><strong>Last Login: </strong><?php echo date(DATE_FORMAT, strtotime($userinfo->lastlogin));?></li>