Why Bootstrap 4 datepicker API doesn't work?

Hello I did some tests and the problem is in using INPUT you should use DIV in datetimer, I think there is a better library than that of bootstrap you are using, try is here jQuery.{.

But anyway so it worked just try to adapt to the look you want.

$('#datepicker').datepicker();
$('#datepicker').on('changeDate', function(e){
    $date = $('#datepicker').datepicker('getDate');
		console.log($date);
});

<!-- Bootstrap CND -->
	<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
  <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
	<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
	<!-- Datapicker css -->
	<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.8.0/css/bootstrap-datepicker.css">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.8.0/js/bootstrap-datepicker.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.8.0/locales/bootstrap-datepicker.pt.min.js"></script>
  <link href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet">

<div class="container-fluid">
  <div class="row">
    <div class="col-md-3">
	    <div class="input-group date" data-provide="datepicker" id="sandbox-container" style="flex: 0 0 auto;">
			<div id="datepicker" data-date-format="dd/mm/yyyy" data-date-autoclose="true" data-date-today-highlight="true"></div>
			<div class="input-group-addon" style="justify-content: center;align-items: center;flex: 0 0 25px;">
				<i class="fa fa-calendar" aria-hidden="true" style="align-self: stretch"></i>
			</div>
		</div>
	  </div>
  </div>
</div>

[Quasi-Solved]

Data API Like the bootstrap plug-ins themselves, datepicker provides a data API that can be used to instantiate datepickers without the need for custom javascript. For most datepickers, simply set data-provide = "datepicker" on the element you want to boot, and it will boot lazily, in the form of true bootstrap.

[unresolved] - in these cases I still don't know what jQuery code waits for datepicker to boot. I tried

$('.datepicker').ready(function() {
            $('.datepicker').datepicker();
            $('#sandbox-container input').datepicker({
            format: "dd/mm/yyyy"
            }).on('changeDate', function(e) {
            $date = $('.datepicker').datepicker('getDate');
            console.log($date);
            });
        });

[debbuging] - enters the function given in ready, but does not execute options or events.

[revolved] -for in-line, use data-provide = "datepicker-inline"; these will be initialized immediately on page load and cannot be loaded lazily.

In this way by changing the HTML

<div class="input-group date" data-provide="datepicker-inline" id="sandbox-container" style="flex: 0 0 auto;">

$(document).ready(function() {
        $('#sandbox-container input').datepicker({
        format: "dd/mm/yyyy"
        }).on('changeDate', function(e) {
        console.log('Aqui');
        $date = $('.datepicker').datepicker('getDate');
        console.log($date);
        });
    });