SO jQuery Fiddle
Test Fiddle mainly for SO Questions jQuery 1.4.3, UI 1.8.5
by Nick Craver
HTML
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/themes/ui-lightness/jquery-ui.css">
<p>Date: <input type="text" id="datepicker"></p>
CSS
.ui-datepicker-week-end, .ui-datepicker-week-end a.ui-state-default {color:red;}
JavaScript
$( "#datepicker" ).datepicker();