public function getEffectiveTriggerTime()
    {
        $trigger = $this->TRIGGER;
        if (!isset($trigger['VALUE']) || 'DURATION' === strtoupper($trigger['VALUE'])) {
            $triggerDuration = VObject\DateTimeParser::parseDuration($this->TRIGGER);
            $related = (isset($trigger['RELATED']) && 'END' == strtoupper($trigger['RELATED'])) ? 'END' : 'START';

            $parentComponent = $this->parent;
            if ('START' === $related) {
                if ('VTODO' === $parentComponent->name) {
                    $propName = 'DUE';
                } else {
                    $propName = 'DTSTART';
                }

                $effectiveTrigger = $parentComponent->$propName->getDateTime();
                $effectiveTrigger = $effectiveTrigger->add($triggerDuration);
            } else {
                if ('VTODO' === $parentComponent->name) {
                    $endProp = 'DUE';
                } elseif ('VEVENT' === $parentComponent->name) {
                    $endProp = 'DTEND';
                } else {
                    throw new InvalidDataException('time-range filters on VALARM components are only supported when they are a child of VTODO or VEVENT');
                }

                if (isset($parentComponent->$endProp)) {
                    $effectiveTrigger = $parentComponent->$endProp->getDateTime();
                    $effectiveTrigger = $effectiveTrigger->add($triggerDuration);
                } elseif (isset($parentComponent->DURATION)) {
                    $effectiveTrigger = $parentComponent->DTSTART->getDateTime();
                    $duration = VObject\DateTimeParser::parseDuration($parentComponent->DURATION);
                    $effectiveTrigger = $effectiveTrigger->add($duration);
                    $effectiveTrigger = $effectiveTrigger->add($triggerDuration);
                } else {
                    $effectiveTrigger = $parentComponent->DTSTART->getDateTime();
                    $effectiveTrigger = $effectiveTrigger->add($triggerDuration);
                }
            }
        } else {
            $effectiveTrigger = $trigger->getDateTime();
        }

        return $effectiveTrigger;
    }