Предпринятый для чтения или защищенная от записи память

$('#datetimepicker').datetimepicker();

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-datetimepicker/2.5.20/jquery.datetimepicker.full.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/jquery-datetimepicker/2.5.20/jquery.datetimepicker.min.css" />

<div class="input-group">
    <input type="text" id="datetimepicker" class="form-control" name="date">
    <label class="input-group-addon btn" for="date">
       <span class="fa fa-calendar open-datetimepicker"></span>
    </label>
</div>