function make_timestamp($year, $month=1, $day=1, $hour=0, $minute=0, $second=0, $timezone=99, $applydst=true) {

    $passedtimezone = $timezone;

    $strtimezone = NULL;

    if (!is_numeric($timezone)) {

        $strtimezone = $timezone;

    }

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {

        $time = mktime((int)$hour, (int)$minute, (int)$second, (int)$month, (int)$day, (int)$year);

    } else {

        $time = gmmktime((int)$hour, (int)$minute, (int)$second, (int)$month, (int)$day, (int)$year);

        $time = usertime($time, $timezone);

        if ($applydst && ($passedtimezone == 99 || !is_numeric($passedtimezone))) {

            $time -= dst_offset_on($time, $strtimezone);

        }

    }

    return $time;

}

in userdate(): 

... // added if clause

    if ($timezone == 99 || !is_numeric($timezone)) {

        $date += dst_offset_on($date, $strtimezone);

    }

...