SO fiddle

Test Fiddle mainly for SO Questions

by Nick Craver

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
<p>Date: <input type="textbox" id="datepicker" /></p>

JavaScript

var ranges = [ { start: new Date(2010, 8, 1), end: new Date(2010, 8, 20) },
               { start: new Date(2010, 9, 1), end: new Date(2010, 9, 20) },
               { start: new Date(2010, 10, 1), end: new Date(2010, 10, 20) } ];

$(function() {
  $("#datepicker").datepicker({
    numberOfMonths: 1,
    beforeShowDay: function(date) {
        for(var i=0; i<ranges.length; i++) {
          if(date >= ranges[i].start && date <= ranges[i].end) return [true, ''];
        }
        return [false, ''];
    },
    minDate: ranges[0].start,
    maxDate: ranges[ranges.length -1].end
  });
});