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

if (hours >= 6 && hours < 9)
{
{document.write("an diesem Morgen")}
}

if (hours >= 9 && hours < 12)
{
{document.write("an diesem Vormittag")}
}

if (hours >= 12 && hours < 13)
{
{document.write("zur Mittagszeit")}
}

if (hours >= 13 && hours < 18)
{
{document.write("an diesem Nachmittag")}
}

if (hours >= 18 && hours < 21)
{
{document.write("an diesem Abend")}
}
if (hours >= 21 && hours <= 23)
{
{document.write("in dieser Nacht")}
}

if (hours >= 0 && hours < 6)
{
{document.write("in dieser Nacht")}
}