This solution may help.
$(document).ready(function () {_x000D_
var userLang = navigator.language || navigator.userLanguage;_x000D_
_x000D_
var options = $.extend({},_x000D_
$.datepicker.regional["ja"], {_x000D_
dateFormat: "yy/mm/dd",_x000D_
changeMonth: true,_x000D_
changeYear: true,_x000D_
highlightWeek: true_x000D_
}_x000D_
);_x000D_
_x000D_
$("#japaneseCalendar").datepicker(options);_x000D_
});
_x000D_
#ui-datepicker-div {_x000D_
font-size: 14px;_x000D_
}
_x000D_
<!DOCTYPE html>_x000D_
<html>_x000D_
<head>_x000D_
<meta charset="UTF-8">_x000D_
<link rel="stylesheet" type="text/css"_x000D_
href="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/themes/smoothness/jquery-ui.min.css">_x000D_
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>_x000D_
<script src="https://code.jquery.com/ui/1.12.1/jquery-ui.min.js"></script>_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.11.1/i18n/jquery-ui-i18n.min.js"></script>_x000D_
</head>_x000D_
<body>_x000D_
<h3>Japanese JQuery UI Datepicker</h3>_x000D_
<input type="text" id="japaneseCalendar"/>_x000D_
_x000D_
</body>_x000D_
</html>
_x000D_