sfGuardUserProfile.php

    /**
     * Convert date/time to user's timezone
     *
     * @access public
     * @param mixed $dateTime
     * @param string $format
     * @return string
     */
    public function toUserTimezone($dateTime, $format) {
        //validate date/time value
        if($dateTime === null)
            return null;

        //set default format and server timezone values, don't include timezone
        $df = 'Y-m-d H:i:s';
        $tz = self::getTimezone();

        //convert to date/time default format first
        $dateTime = $dateTime instanceof DateTime ? date($df, $dateTime->format("U")) : ensureDateTime($dateTime, $df);

		//re-validate the date/time string to make sure we can use
		if(isValidDateTime($dateTime) === false)
			return $dateTime; //catches edge cases where strings like "Never" are passed

        //if invalid timezone, then do not convert
        //remember that by design date/time always converted from server time to user time
        //so if timezone if invalid, then we should just return original value in a requested format
        if(!in_array($tz, DateTimeZone::listIdentifiers()))
            return date($format, strtotime($dateTime));

        //initialize date/time object using server's timezone
        $dt = new DateTime($dateTime);
        $dt->setTimezone(new DateTimeZone($tz));

		Debug::toLog($dt);
		Debug::toLog(date("Y-m-d H:i:s", $dt->format($format)));

        //return converted date/time value
        return $dt->format($format);
    }