Datetimepicker setDate issue

https://github.com/trentrichardson/jQuery-Timepicker-Addon/issues/686

HTML

<link rel="stylesheet" href="http://trentrichardson.com/examples/timepicker/jquery-ui-timepicker-addon.css">
<script src="http://trentrichardson.com/examples/timepicker/jquery-ui-timepicker-addon.js"></script>
<input id="date"/>

<a id="test" href="#">test</a>

JavaScript

$.datepicker.setDefaults({
    formatDate: 'd/m/Y',
});

$("#date").datetimepicker();
$("#date").datepicker("setDate", "1/1/2018");
$("#test").click(function(){
    
});