<div class="form-group" ng-repeat="item in items">
        <div class="row" style="margin: 15px 0px;">
            <div class="col-md-6 col-lg-6 col-sm-6" style="padding-left:0">

                <label>Start Date</label>
                <p class="input-group">
                    <input type="text" class="form-control" datetime-picker="dd/MM/yyyy" enable-time="false" ng-model="item['start_date'+$index]" is-open="['start_date'+$index].open"  />

                    <span class="input-group-btn">
                        <button type="button" class="btn btn-default" ng-click="openCalendar($event, 'start_date',$index)"><i class="fa fa-calendar"></i></button>
                    </span>
                </p>

            </div>
      </div>
</div>
    <button ng-click="add()">Add New Row</button>

$scope.items = [];
    $scope.add = function() {
        $scope.items.push({
            start_date:"",
            start_time:"",
            end_date:"",
            end_time:""

        });
    }
    $scope.openCalendar = function(e,picker,index) {
        console.log('index',index);
           console.log('picker',picker);
        var picker_index=picker+index;
        console.log($scope[picker_index])
        $scope.[picker_index]open = true;
        console.log( $scope[picker][index])
    };