CSS Fix

[css] .ui-datepicker.ui-datepicker-multi {
z-index: 50 !important;
}
[/css]

Code Fix

[javascript] <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js"></script>
<script>
jQuery(function() {
jQuery( "#field2" ).datepicker({
dateFormat: "DD, MM d, yy",
numberOfMonths: 2,
showButtonPanel: true
});
});

</script>
[/javascript]