Can't change the time zone in one of the .php pages?

Question

PHP

Good afternoon! The problem is the following, I do not understand how to change the time zone on the page with notifications.
Now I will give an example with a chat, where the time zone works adequately + 4 hours. where is the $date variable, the string is called time in the database

<?php 

ULogin(1);
date_default_timezone_set('Europe/Samara');
$date = date("Y-m-d G:i:s");
if ($_POST['enter'] and $_POST['text']) {
$_POST['text'] = FormChars($_POST['text']);
mysqli_query($CONNECT, "INSERT INTO `chat`  VALUES ('', '$_POST[text]', '$_SESSION[USER_LOGIN]', '$date')");
exit(header('location: /chat'));

}

Head('Чат');
?>

Now the code that does not want to change the time zone. In the database, it is written as 0000000.
First, I registered it in index.php, that is, I took out the date before the start of the session. (I also set it before the start of the function)

<?php
date_default_timezone_set('Europe/Samara');
$date = date("Y-m-d G:i:s");
include_once 'setting.php';
session_start();

Then I wrote a function in the same file. Before $date was NOW(), but with it -4h

function SendNotice($p1, $p2) {
global $CONNECT;
$Row = mysqli_fetch_assoc(mysqli_query($CONNECT, "SELECT `id` FROM `users` WHERE `login` = '$p1'"));
if (!$Row['id']) echo 'Error';
mysqli_query($CONNECT, "INSERT INTO `notice` VALUES ('', '$Row[id]', 0, '$date', '$p2')");
}

I included the page and here is the code where the requests themselves occur. I throw only him, because. date doesn't appear anywhere else

if (!$Module or $Module == 'notice') {
$Param1 = "SELECT `id`, `status`, `date`, `text` FROM `notice` WHERE `uid` = $_SESSION[USER_ID] ORDER BY `id` DESC LIMIT 0, 5";
$Param2 = "SELECT `id`, `status`, `date`, `text` FROM `notice` WHERE `uid` = $_SESSION[USER_ID] ORDER BY `id` DESC LIMIT START, 5";
$Param3 = "SELECT COUNT(`id`) FROM `notice`";
$Param4 = "/notice/?page=";
}

And you know what's most interesting? If you write <?=date("Ymd G:i:s")?> in the futor, it shows the correct time zone!
In the database, date has type datetime