JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.7.0/themes/base/jquery-ui.css">
<div id="status">Selected date: none</div>

<button id="btn">Select a date before clicking me</button>
<br />
<input type="text" id="dp" />

JavaScript

$(function() {

    $("#dp").datepicker({
        onSelect: function(currDate) {
            $("#status").html("Selected date: " + currDate);
        }
    });

    $("#btn").click(function() {
        $(this).html("Increment date by one day and fire onSelect");
        /* Increment the date by one day */
        var currentDate = $("#dp").datepicker("getDate");
        var newDate = new Date(currentDate);
        newDate.setDate( currentDate.getDate() + 1);
        $("#dp").datepicker("setDate", newDate);

        /* This is your function */
        var onSelectFunction = $("#dp").datepicker("option","onSelect");

        /* How your datepicker instance is set to format its date on select */
        var format  = $("#dp").datepicker( "option", "dateFormat" );

        /* Make the "currDate" parameter as jQuery would do on select */
        var currDate = $.datepicker.formatDate(format,newDate)

        /* Fire the callback */
        onSelectFunction( currDate );
    });
});