How to set time zone in codeigniter?

If you are looking globabally setup timezone in whole project then you can setup it CI application/config.php file

$config['time_reference'] = 'Asia/Dubai';

Placing this date_default_timezone_set('Asia/Kolkata'); on config.php above base url also works

PHP List of Supported Time Zones

application/config/config.php

<?php

defined('BASEPATH') OR exit('No direct script access allowed');

date_default_timezone_set('Asia/Kolkata');

Another way I have found use full is if you wish to set a time zone for each user

Create a MY_Controller.php

create a column in your user table you can name it timezone or any thing you want to. So that way when user selects his time zone it can can be set to his timezone when login.

application/core/MY_Controller.php

<?php

class MY_Controller extends CI_Controller {

    public function __construct() {
        parent::__construct();
        $this->set_timezone();
    }

    public function set_timezone() {
        if ($this->session->userdata('user_id')) {
            $this->db->select('timezone');
            $this->db->from($this->db->dbprefix . 'user');
            $this->db->where('user_id', $this->session->userdata('user_id'));
            $query = $this->db->get();
            if ($query->num_rows() > 0) {
                date_default_timezone_set($query->row()->timezone);
            } else {
                return false;
            }
        }
    }
}

Also to get the list of time zones in php

 $timezones =  DateTimeZone::listIdentifiers(DateTimeZone::ALL);

 foreach ($timezones as $timezone) 
 {
    echo $timezone;
    echo "</br>";
 }

Add this line inside the main index.php of codeigniter folder

date_default_timezone_set('Asia/Kolkata');