Datepicker Utilities

Datepicker Utilities


I'm a little new to jQuery so maybe its a simple answer, but how do
you use datepicker utilities?
I'm trying to use formatDate and without success:
$(function () {
    $.datepicker.formatDate('yy-mm-dd'); //set format
    $("#dateinput").datepicker(
        {
            rangeSelect: true,
            onSelect: function(dateText) {
                $('#rangedate').val(dateText);
            }
        }
    );
});