var today = new Date();
var styledoc = 'sabah.css';
if((today.getHours() < 5) && (today.getHours() > 19)){ //Akşam 8den sabah 5e kadar
styledoc ='gece.css';
}elseif((today.getHours() < 20) && (today.getHours() > 12)){ //Öğlen 1den akşam 8e kadar
styledoc ='oglen.css';
}
var headID = document.getElementsByTagName("head")[0];
var cssNode = document.createElement('link');
cssNode.type = 'text/css';
cssNode.rel = 'stylesheet';
cssNode.href = styledoc;
cssNode.media = 'screen';
headID.appendChild(cssNode);