Facebook Timezone Confusion

/**
 * Automates the process of correcting times imported from Facebook by a fixed
 * number of hours (plus or minus).
 *
 * @uses DateTime which introduces a requirement for PHP 5.2 or greater
 */
class FBEventsTimeCorrection {
        protected $negative = false;
        protected $hours = 0;
        protected $modifier = '';
        protected $eventData = array();
        const CORRECTION_FORMAT = '#^([\\+-]?)(\\d{1,2})$#';


        /**
         * Sets up automated correction of imported Facebook event times.
         *
         * The correction should be specified in the form of an optional positive or
         * negative operator (+/-) followed by an integral number in the range 0-12,
         * such as +11 or -7.
         *
         * If not preceded by a positive/negative operator then positive is assumed.
         *
         * @param string $correction
         * @throws Exception
         */
        public function __construct($correction) {
                if ($this->setCorrection($correction))
                        add_filter('tribe_fb_parse_facebook_event', array($this, 'applyCorrection'));

                else throw new Exception('The specified correction cannot be understood.');
        }


        /**
         * Tests to see if the specified correction is in an understandable format.
         *
         * @param string $correction
         * @return bool
         */
        public function setCorrection($correction) {
                $matches = array();

                // Test to see if a basic format of [+/-]n has been specified then try to set
                if (preg_match(self::CORRECTION_FORMAT, $correction, $matches) === 1) {
                        if (count($matches) !== 3) return false;
                        else return $this->setDirectionAndHours($matches[1], $matches[2]);
                }

                return false;
        }


        /**
         * Sets the internal variables used to record the correction.
         *
         * If the $hours param is out of bounds this method will return bool false.
         *
         * @param $direction
         * @param $hours
         * @return bool
         */
        protected function setDirectionAndHours($direction, $hours) {
                // Do we have a negative operator?
                if ($direction === '-') $this->negative = true;

                // Extract the number of hours and ensure they are within range
                $this->hours = (int) $hours;
                if ($this->hours < 0 or $this->hours > 12) return false;

                return true;
        }


        /**
         * Attempts to adjust the event date/time.
         *
         * Although we require the DateTime class (available as of PHP 5.2) we will
         * degrade gracefully for earlier versions of PHP and give an opportunity
         * for a replacement class to be used on those versions (ie, from PEAR).
         *
         * @param array $eventData
         * @return array
         */
        public function applyCorrection($eventData) {
                if (class_exists('DateTime')) {
                        $this->correctDateTime('Start', $eventData);
                        $this->correctDateTime('End', $eventData);
                }

                return $eventData;
        }


        /**
         * Performs the correction of event date/time.
         *
         * @param $modifier
         * @param $eventData
         */
        protected function correctDateTime($modifier, &$eventData) {
                $this->modifier = $modifier;
                $this->eventData = $eventData;

                $datetime = $this->getDateTimeObject();
                $datetime->modify($this->getAdjustment());

                $this->rebuildEventData($datetime);
                $eventData = $this->eventData;
        }


        /**
         * Creates a DateTime object based on the Start|End date/time. Whether it
         * is the Start or End is determined by the $modifier property.
         *
         * @return DateTime
         */
        protected function getDateTimeObject() {
                $date = $this->eventData["Event{$this->modifier}Date"];
                $hour = $this->eventData["Event{$this->modifier}Hour"];
                $minute = $this->eventData["Event{$this->modifier}Minute"];
                $meridian = $this->eventData["Event{$this->modifier}Meridian"];

                // Convert hour to 24hr format
                if ($meridian === 'PM') $hour += 12;
                $hour = sprintf('%02d', $hour);
                $minute = sprintf('%02d', $minute);

                return new DateTime("$date $hour:$minute:00");
        }


        /**
         * Generates a strtotime() compatible modifier string.
         *
         * @return string
         */
        protected function getAdjustment() {
                $adjustment = '';

                if ($this->negative) $adjustment .= '-';
                $adjustment .= $this->hours.' hours';

                return $adjustment;
        }


        /**
         * Rebuilds the event data array with our adjusted date/time.
         */
        protected function rebuildEventData(DateTime $datetime) {
                $this->eventData["Event{$this->modifier}Date"] = $datetime->format('Y-m-d');
                $this->eventData["Event{$this->modifier}Hour"] = $datetime->format('g');
                $this->eventData["Event{$this->modifier}Minute"] = $datetime->format('i');
                $this->eventData["Event{$this->modifier}Meridian"] = $datetime->format('A');
        }
}

/**
 * Here we are enforcing an adjustment of -5hrs. If instead 
 * we wanted the imported times to be set 4hrs ahead we would
 * use +4, etc.
 */
new FBEventsTimeCorrection('-5');