gistfile1.txt

add_filter( 'propertyhive_property_query_meta_query', 'exclude_completed_more_than_six_months', 10, 2 );
function exclude_completed_more_than_six_months($meta_querys, $q)
{
	$meta_querys[] = array(
        'relation' => 'OR',
        array(
            'key'     => '_completion_date',
            'compare' => 'NOT EXISTS'
        ),
        array(
            'key'     => '_completion_date',
            'value'   => '',
            'compare' => '='
        ),
        array(
            'key'     => '_completion_date',
            'value'   => date("Y-m-d", strtotime('6 months ago')),
            'compare' => '>='
        )
    );

	return $meta_querys;
}