Just a simple jQueryUI based datepicker

datepicker-example.js

<!-- This is the form element that will be transformed into a datepicker -->
<div type="text" id="ScheduleDate style="float:left;margin-left:15px">

<!-- This script finds the above datepicker and when a day is selected goes to the current url with a different date -->
<!--  EXAMPLE: http://YourServer/Schedule.php?date=2012-01-13 -->
<script>
  $(function() {
    $("#ScheduleDate").datepicker({
      onSelect: function(dateText, inst) { window.location.href = location.href.substring(0,location.href.lastIndexOf("?"))+"?date="+dateText},
    });
  });
</script>