JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://code.jquery.com/ui/1.8.20/themes/base/jquery-ui.css">
<input type="text" value="" id="date" name="foo">

JavaScript

$(function() {
    $.datepicker._updateDatepicker_original = $.datepicker._updateDatepicker;
    $.datepicker._updateDatepicker = function(inst) {
        $.datepicker._updateDatepicker_original(inst);
        var afterShow = this._get(inst, 'afterShow');
        if (afterShow)
            afterShow.apply((inst.input ? inst.input[0] : null), [inst]);
    }
});

$("#date").datepicker({
    onSelect: function(selectedDate, inst) {
        showDateInTitle(inst);
    },
    afterShow: function (inst) {
        showDateInTitle(inst);
    }
});

function showDateInTitle(picker) {
    console.log(picker.selectedDay);
    console.log(new Date().getDate());
    var span = picker.dpDiv[0].querySelector('.ui-datepicker-day'),
        df, month;
    if (span === null) {
        month = picker.dpDiv[0].querySelector('.ui-datepicker-month');
        if (!month) return;
        span = document.createElement('span');
        span.setAttribute('class', 'ui-datepicker-day');
        df = document.createDocumentFragment();
        df.appendChild(span);
        df.appendChild(document.createTextNode('\u00a0'));
        month.parentNode.insertBefore(
            df,
            month
        );
    }
    span.textContent = 'Hi';
}