guarda questo:
codice:
 
<head>

<script type="text/javascript" language="JavaScript">
<!--



        var now = new Date();
        var hours = now.getHours();
	var psj=0;

	//18-19 night
        if (hours > 17 && hours < 20){
		document.write('<body bgcolor="orange" text="#FFFFFF">')
	}

	//20-21 night
        if (hours > 19 && hours < 22){
		document.write('<body bgcolor="orangered" text="#FFFFFF">')
	}

	//22-4 night
        if (hours > 21 || hours < 5){
		document.write('<body bgcolor="black" text="#FFFFFF">')
	}

	//9-17 day
        if (hours > 8 && hours < 18){
		document.write('<body bgcolor="deepskyblue" text="#FFFFFF">')
	}

	//7-8 day
        if (hours > 6 && hours < 9){
		document.write('<body bgcolor="skyblue" text="#FFFFFF">')
	}

	//5-6 day
        if (hours > 4 && hours < 7){
		document.write('<body bgcolor="steelblue" text="#FFFFFF">')
	}
//-->
</script>


</head>