I have problem with original settings, because can't set Country for time zone. I must two time in year change timezone setting because DST.

Here is a change for better work with DST and timezones.

/include/campsite_init.php

// set timezone
$timeZone = SystemPref::Get('TimeZone');
if (!empty($timeZone)) {
    date_default_timezone_set($timeZone);
    $g_ado_db->Execute("SET SESSION time_zone = '" . date('P') . "'");
} else {
    // Some people forget to set their timezone in their php.ini,
    // this prevents that from generating warnings
    @date_default_timezone_set(@date_default_timezone_get());
    //set timezone for mysql session
    $g_ado_db->Execute("SET SESSION time_zone = '" . date('P') . "'");

}
unset($timeZone);

/admin-files/system_pref/index.php

        <?php
       
        $timeZoneCities = array(
            0 => 'London, Lisbon, Casablanca',
            1 => 'Brussels, Copenhagen, Madrid, Paris',
            2 => 'Athens, Istanbul, Jerusalem',
            3 => 'Baghdad, Riyadh, Moscow, St. Petersburg',
            4 => 'Abu Dhabi, Muscat, Baku, Tbilisi',
            5 => 'Ekaterinburg, Islamabad, Karachi, Tashkent',
            6 => 'Almaty, Dhaka, Colombo',
            7 => 'Bangkok, Hanoi, Jakarta',
            8 => 'Beijing, Perth, Singapore, Hong Kong',
            9 => 'Tokyo, Seoul, Osaka, Sapporo, Yakutsk',
            10 => 'Eastern Australia, Guam, Vladivostok',
            11 => 'Magadan, Solomon Islands, New Caledonia',
            12 => 'Auckland, Wellington, Fiji, Kamchatka',
            -1 => 'Azores, Cape Verde Islands',
            -2 => 'Mid-Atlantic',
            -3 => 'Brazil, Buenos Aires, Georgetown',
            -4 => 'Atlantic Time (Canada), Caracas, La Paz',
            -5 => 'Eastern Time (US & Canada), Bogota, Lima',
            -6 => 'Central Time (US & Canada), Mexico City',
            -7 => 'Mountain Time (US & Canada)',
            -8 => 'Pacific Time (US & Canada)',
            -9 => 'Alaska',
            -10 => 'Hawaii',
            -11 => 'Midway Island, Samoa',
            -12 => 'Eniwetok, Kwajalein',
        );
       
        $timeZone = SystemPref::Get('TimeZone');
        camp_html_select_option('', $timeZone, getGS('disabled'));
        for ($k = -12; $k < 13; $k++) {
            $v = $k < 0 ? $k : '+' . $k;
            if ($timeZoneCities[$k] != '') camp_html_select_option('Etc/GMT'.$v, $timeZone, "GMT $v:00 ({$timeZoneCities[$k]})");
            else camp_html_select_option($v, $timeZone, "GMT $v:00");
        }

        foreach(timezone_identifiers_list() as $tz) {
            camp_html_select_option($tz, $timeZone, $tz);
        }
        ?>




Settting the timezone in php.ini is usable too (works with DST), but original code not set the timezone for mysql session. This issue is solved too.