<script> <!-- function getStylesheet() { var currentTime = new Date().getHours(); if (0 <= currentTime&¤tTime < 5) { document.write("<link rel='stylesheet' href='night.css' type='text/css'>"); } if (5 <= currentTime&¤tTime < 11) { document.write("<link rel='stylesheet' href='morning.css' type='text/css'>"); } if (11 <= currentTime&¤tTime < 16) { document.write("<link rel='stylesheet' href='day.css' type='text/css'>"); } if (16 <= currentTime&¤tTime < 22) { document.write("<link rel='stylesheet' href='evening.css' type='text/css'>"); } if (22 <= currentTime&¤tTime <= 24) { document.write("<link rel='stylesheet' href='night.css' type='text/css'>"); } } getStylesheet(); --> </script> <noscript><link href="main.css" rel="stylesheet"></noscript>

Name your css files accordingly: night.css, day.css, etc… One cool bonus is that since JavaScript gets the time from the local machine instead of from the server, users will be served the time-based stylesheet based on their time, not the server’s, which may be in a completely different timezone.

If JavaScript is disabled in the browser, it will default to the main.css stylesheet.