Fire the datepicker onselect event manually

Question

Can anyone tell me how do you trigger the onselect event of datepicker? My code is working well (pulling some data from a database based on the value of datepickers altfield) but when the page loads it doesn't trigger the onselect event on the current date and it doesn't display anything; so I would like to do that manually.

<script>
     $( "#datepicker" ).datepicker
    (
    {
          altField: '#sheet',
          onSelect: function load() {
            $(document).ready(function() {
                    $.ajax({
                    type: 'POST',
                    url: 'test.php',
                    data: {sheetid: $('#sheet').val()},
                    success: function(data)
                    {
                        $("#content").html(data);
                    }
                });

        });
        },
          firstDay: 1});
    </script>

Answer 1

This is the only solution I found that also works for a datetimepicker

var $calendar =$('#from');
$.datepicker._getInst($calendar[0]).settings.onSelect()//or onClose or any event