add_filter( 'aioseo_local_business_output_opening_hours_data', 'aioseo_change_local_business_output_opening_hours_data', 10, 3 );

function aioseo_change_local_business_output_opening_hours_data( $openingHoursData, $instance, $postId ) {

	$openingHoursData->labels->closed = __( 'Closed today.' );

	return $openingHoursData;

}