JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.9.2/themes/redmond/jquery-ui.css">
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.9.2/jquery-ui.min.js"></script>
<input />

JavaScript

function IsChristmas(date) {
    var day = date.getDate();
    var month = date.getMonth() + 1;
    return (day === 25 && month === 12);
}

function IsNewYearsDay(date) {
    var day = date.getDate();
    var month = date.getMonth() + 1;
    return (day === 1 && month === 1);
}

$('input').datepicker({
    beforeShowDay: function (date) {
        return [(!IsChristmas(date) && !IsNewYearsDay(date))];
    }
});