angular datepicker instance for multiple datepickers

gistfile1.txt

  html
    <p class="input-group">
    <input type="text" class="form-control" datepicker-popup="{{format}}"  ng-model="latestRevision(dValue).date_returned" close-text="Close" datepicker-options="datePicker.options"  is-open="datePicker.instances['returned'+dValue.document_id]" />
        <span class="input-group-btn">
            <button type="button" class="btn btn-sm btn-default no-border" datepicker-options="datePicker.options"  close-text="Close" ng-click="datePicker.open($event, 'returned'+dValue.document_id)"><i class="fa fa-calendar"></i></button>
        </span>
  </p>
  
  js
  $scope.datePicker = (function() {
    var method = {};
    method.instances = [];

    method.open = function($event, instance) {
      $event.preventDefault();
      $event.stopPropagation();

      method.instances[instance] = true;
    };

    method.options = {
      'show-weeks': false,
      startingDay: 0
    };

    method.format = 'dd/MM/yyyy';

    return method;
  }());