How to increase the post and comment date in a MYSQL database

$sql_conn = mysql_connect('serwer.com', 'admin', 'passwd');
$sql = "UPDATE `wp_posts` SET `post_date`=NOW(), `post_date_gmt`=NOW()";
mysql_close($sql_conn);

<?php
function change_date($date1)
	{
	$date2=strtotime($date1) + (60 * 60 * 24);
	return date("Y-m-d H:i:s",$date2);
	}

$dbuser="root";
$dbpass="";
$dbname="blog";
$handle = mysql_connect("localhost", $dbuser, $dbpass) 
    or die("Connection Failure to Database");
//echo "Connected to database server<br>";
mysql_select_db($dbname, $handle) or die ($dbname . " Database not found." . $dbuser);
//echo "Database " .  $database . " is selected<br><br>";



$query = "SELECT * FROM `wp_posts`";
$run_query = mysql_query($query);

while ($row = mysql_fetch_row($run_query))
	{
	$new_date1=change_date($row[2]);
	$new_date2=change_date($row[3]);
	
	$query = "UPDATE wp_posts SET post_date='$new_date1', post_date_gmt='$new_date2' WHERE ID='$row[0]'";
	
	mysql_query($query )or die("Error");
	} 
mysql_close($handle);
?>

$query = "SELECT * FROM `wp_comments`";
$run_query = mysql_query($query);

while ($row = mysql_fetch_row($run_query))
    {
    $new_date1=change_date($row[7]);
    $new_date2=change_date($row[8]);
    
    $query = "UPDATE wp_comments SET comment_date='$new_date1', comment_date_gmt='$new_date2' WHERE comment_ID='$row[0]'";
    
    mysql_query($query )or die("Error");
    }

$query = "SELECT * FROM `wp_comments`";
$run_query = mysql_query($query);

while ($row = mysql_fetch_row($run_query))
    {
    $new_date1=change_date($row[6]);
    $new_date2=change_date($row[7]);
    
    $query = "UPDATE wp_comments SET comment_date='$new_date1', comment_date_gmt='$new_date2' WHERE comment_ID='$row[0]'";
    
    mysql_query($query )or die("Error");
    }