src/Extensions/SiteTreeContentReview.php
public function getReviewDate(SiteTree $page = null)
    {
        if ($page === null) {
            $page = $this->owner;
        }

        if ($page->obj('NextReviewDate')->exists()) {
            return $page->obj('NextReviewDate');
        }

        $options = $this->owner->getOptions();

        if (!$options) {
            return false;
        }

        if (!$options->ReviewPeriodDays) {
            return false;
        }

        // Failover to check on ReviewPeriodDays + LastEdited
        $nextReviewUnixSec = strtotime(' + ' . $options->ReviewPeriodDays . ' days', DBDatetime::now()->getTimestamp());
        $date = DBDate::create('NextReviewDate');
        $date->setValue($nextReviewUnixSec);
        return $date;
    }
public function getReviewDate(SiteTree $page = null)
    {
        if ($page === null) {
            $page = $this->owner;
        }

        if ($page->obj('NextReviewDate')->exists()) {
            return $page->obj('NextReviewDate');
        }

        $options = $this->owner->getOptions();

        if (!$options) {
            return false;
        }

        if (!$options->ReviewPeriodDays) {
            return false;
        }

        // Failover to check on ReviewPeriodDays + LastEdited
        $nextReviewUnixSec = strtotime(' + ' . $options->ReviewPeriodDays . ' days', DBDatetime::now()->getTimestamp());
        $date = DBDate::create('NextReviewDate');
        $date->setValue($nextReviewUnixSec);
        return $date;
    }
Returns false if the content review have disabled.

@param SiteTree $page

@return bool|DBDate