Views Nested Condition Group

module_name.php

<?php

function adw_calendar_query_views_events_list_alter(Drupal\Core\Database\Query\AlterableInterface $query){


        if(
            $query->getMetaData('view')->getDisplay()->display['id'] == 'page_1'
            || $query->getMetaData('view')->getDisplay()->display['id'] == 'page_2'
        ){

            // Get the filters set for the date range
            $dateFilter = $query->getMetaData('view')->exposed_data['date'];
            $startFilterFormatted = date('Y-m-d',strtotime($dateFilter['min']));
            $endFilterFormatted = date('Y-m-d',strtotime($dateFilter['max']));

            // Get the second condition which is the one we're interested in.
            $conditions =& $query->conditions()[0]['field']->conditions()[1]['field'];

            // Create a new conditions group
            $newConditionGroup = $query->andConditionGroup()
                ->condition('node__field_event_start_date.field_event_start_date_value', $startFilterFormatted, '<')
                ->condition('node__field_event_end_date.field_event_end_date_value', $endFilterFormatted, '>')
            ;

            // Add our new condition group to the second condition
            $conditions->condition($newConditionGroup);

        }
    }

?>