Keep in mind, the jQuery UI's datepicker is not initialized with datetimepicker(), there appears to be a plugin/addon here: http://trentrichardson.com/examples/timepicker/.
However, with just jquery-ui it's actually initialized as $("#example").datepicker(). See jQuery's demo site here: http://jqueryui.com/demos/datepicker/
$(document).ready(function(){
$("#example1").datepicker();
});
To use the datetimepicker at the link referenced above, you will want to be certain that your scripts path is correct for the plugin.