Nein, tut es nicht - zumindest nicht in dieser Variante (ich kenne ja deine Variante nicht).
Doch, tut es :(
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Hello!</title>
<script language="JavaScript" type="text/javascript">
<!--
zeit1 = new Date(2006, 02, 26);
zeit2 = new Date(2006, 03, 05);
diff = Math.round((zeit2.getTime() - zeit1.getTime()) / (1000 * 60 * 60 * 24));
alert(diff);
var zeit3=Date.UTC(2006,02,26);
var zeit4=Date.UTC(2006,03,05);
var diff2 = (zeit4 - zeit3) / (1000 * 60 * 60 * 24);
alert(diff2);
-->
</script>
</head>
<body>
</body>
</html>