I took a bootstrap and jQuery datepicker online since it was easier for me, it worked perfectly on localhost, but now after uploading it online, it doesn't work, I click on the input, and usually a calendar would pop up, now I just have a plain text input.
This is the full file where I use the datepicker:
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet">
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.9.0/moment.min.js"></script>
<link rel="stylesheet" type="text/css" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datetimepicker/4.17.47/css/bootstrap-datetimepicker.min.css">
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datetimepicker/4.17.47/js/bootstrap-datetimepicker.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<link href="css/reservation.css" rel="stylesheet">
</head>
<body>
<section class="book-a-table">
<h1 class="title">Book</h1>
<form action="choose-time.php" class="contact-form row">
<div class="form-field col-lg-6">
<input id="name" class="input-text js-input" name="name" type="text" required>
<label class="label" for="name">Ime</label>
</div>
<div class="form-field col-lg-6 ">
<div class='input-group date' id='datetimepicker1'>
<span class="input-group-addon">
<input type='text'class="form-control input-text js-input" id="date" name="date"/>
</span>
<input class="submit-btn" name="submit" type="submit" value="Choose time >">
</form>
</section>
I had some script for disabling dates, I removed it but I still had no changes, tried to modify it, no changes, I only get a blank input text form.
It might be blocked by your server since it violates the Content Security Policy directive.
Check whether it shows in Browser Console (Ctrl + Shift + i).
Best way is to download Bootstrap files (e.g. https://getbootstrap.com/docs/4.3/getting-started/download/), upload it to your server and add this in your html
<link rel="stylesheet" href="./css/bootstrap.min.css">