Bootstrap datepicker中显示了其他日期

I am using bootstrap datepicker

here is my code

var available_Dates = ["2015-08-05","2015-08-16","2015-08-21"];

$('input.date-pick').datepicker({
    language: 'en',
    beforeShowDay: function(date){
      var formattedDate = $.fn.datepicker.DPGlobal.formatDate(date, 'yyyy-mm-dd', 'en');
      if ($.inArray(formattedDate.toString(), available_Dates) == -1){
          return {
            enabled : false
                };
         }
          return;
      }
});

Html i am using

<div class="form-group">
<label><i class="icon-calendar-7"></i> Select a date</label>
<input class="date-pick form-control" placeholder="Jul 18, Sat" data-date-format="M d, D" type="text">
</div>

Now the problem is, the result comes with an additional day.

• 2015-08-06
• 2015-08-17
• 2015-08-22

But i want selected date to be the result.

Please provide suggestion, Thank you