That code is in UBB file templates/default/island_public_calendar.tpl

So I modified the version on the server as follows:
Code
<script language="javascript" type="text/javascript">
// <![CDATA[
var ubbcal = new Date();
var today = ubbcal.getDay();
day = get_object("day" + today);
currenttitle = day.title;
day.title = "<?php echo $ubbt_lang['TODAY'] ?>\n" + currenttitle;
day.className = "standouttext";
// ]]>
</script>

I then rebuilt the cache so the update would take affect, checked in with Firefox and saw the added two lines.

Now IE8 throws an "Object expected" error on the "day = get_object("day" + today);" line of code.

Further suggestions, please.