Different background color depending on the time of the day

<script type="text/javascript">
    <!--
    var now = new Date();
    var hours = now.getHours();
    var psj=0;
    document.write('<style type="text/css">')
    //18-19 night
    if (hours > 17 && hours < 20){
    document.write('body{background:orange; color:#FFFFFF;} a{color: yellow !important}')
    }
    //20-21 night
    if (hours > 19 && hours < 22){
    document.write('body{background:orangered; color:#FFFFFF;} a{color: yellow !important}')
    }
    //22-4 night
    if (hours > 21 || hours < 5){
    document.write('body{background:black; color:#FFFFFF;} a{color: yellow !important}')
    }
    //9-17 day
    if (hours > 8 && hours < 18){
    document.write('body{background:deepskyblue; color:#FFFFFF;} a{color: yellow !important}')
    }
    //7-8 day
    if (hours > 6 && hours < 9){
    document.write('body{background:skyblue; color:#FFFFFF;} a{color: yellow !important}')
    }
    //5-6 day
    if (hours > 4 && hours < 7){
    document.write('body{background:steelblue; color:#FFFFFF;} a{color: yellow !important}')
    }
    document.write('</style>')
    //-->
    </script>