Unable to use bootstrap date picker

Question 1

You only need to remove #sandbox-container As it is not present in your code.

Try This:

<!DOCTYPE html>
<html>
    <head>
        <title>Bootstrap</title>
        <meta name="viewport" content="width=device-width,initial-scale=1.0">
        <link href="../files/css/bootstrap.min.css" rel="stylesheet">
        <link href="http://eternicode.github.io/bootstrap-datepicker/bootstrap-datepicker/css/datepicker3.css" rel="stylesheet">

        <script src="../files/js/jquery.min.js"></script>
        <script src="../files/js/bootstrap.js"></script>
        <script src="http://eternicode.github.io/bootstrap-datepicker/bootstrap-datepicker/js/bootstrap-datepicker.js"></script>
    </head>
    <body>
        <div class="input-group date">
            <input type="text" class="form-control"><span class="input-group-addon"><i class="glyphicon glyphicon-th"></i></span>
        </div>

<script>
    $('.input-group.date').datepicker({
        format: "yyyy/mm/dd",
        startDate: "2012-01-01",
        endDate: "2015-01-01",
        todayBtn: "linked",
        autoclose: true,
        todayHighlight: true
    });
</script>
    </body>
</html>

Question 2

Move the script include tags above your script, and remove #sandbox-container from your selector - it doesn't exist. It works after that (with correct urls)...

<script src="http://code.jquery.com/jquery-1.11.0.min.js"></script>
<script src="//netdna.bootstrapcdn.com/bootstrap/3.1.1/js/bootstrap.min.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.3.0/js/bootstrap-datepicker.js"></script>
<script>
    $('.input-group.date').datepicker({
        format: "yyyy/mm/dd",
        startDate: "2012-01-01",
        endDate: "2015-01-01",
        todayBtn: "linked",
        autoclose: true,
        todayHighlight: true
    });
</script>

jsfiddle example...

Question 3

You are calling the datepicker function before calling jQuery, bootstrap.js & bootstrap-datepicker.js. If you debug it you will get an exception that tells you "datepicker" is not defined.

Instead you should write :

    <script src="../files/js/jquery.min"></script>
    <script src="../files/js/bootstrap.js"></script>
    <script src="http://eternicode.github.io/bootstrap-datepicker/js/bootstrap-datepicker.js"></script>

    <script>
        $('#sandbox-container .input-group.date').datepicker({
             format: "yyyy/mm/dd",
             startDate: "2012-01-01",
             endDate: "2015-01-01",
             todayBtn: "linked",
             autoclose: true,
             todayHighlight: true
        });
    </script>