You could ssh to your pfSense box (winscp or ctrl+l in ubuntu)
edit /usr/local/www/index.php
make a new line before
<p class="pgtitle">System Overview</p>
and add
<?
exec("/bin/date", $dateOutput, $dateStatus);
$currentDate = $dateOutput[0];
?>
and change
<td width="25%" class="vncellt">Platform</td>
<td width="75%" class="listr"><?=htmlspecialchars($g['platform']);?></td>
to
<td width="25%" class="vncellt">Platform / Current Date </td>
<td width="75%" class="listr"><?=htmlspecialchars($g['platform']);?> / <?=$currentDate;?></td>
Save