diff --git a/lib/Feed.php b/lib/Feed.php
index 6dc6761..bfddb15 100644
--- a/lib/Feed.php
+++ b/lib/Feed.php
@@ -82,17 +82,104 @@ class Feed {
             // If there aren't any of those there is no id.
             $f->id = '';
         }
+        $this->data = $feed;
         // if a feedID is supplied, determine which items are already in the database, which are not, and which might have been edited
         if(!is_null($feedID)) {
-            // FIXME: first perform deduplication on items
-            // array if items in the fetched feed
-            $items = $feed->items;
-            // get as many of the latest articles in the database as there are in the feed
-            $articles = Data::$db->articleMatchLatest($feedID, sizeof($items));
-            // arrays holding new, edited, and tentatively new items; items may be tentatively new because we perform two passes
-            $new = $tentative = $edited = [];
-            // iterate through the articles and for each determine whether it is existing, edited, or entirely new
-            foreach($items as $index => $i) {
+            $this->matchToDatabase($feedID);
+        }
+        return true;
+    }
+
+    protected function deduplicateItems(array $items): array {
+        /* Rationale:
+            Some newsfeeds (notably Planet) include multiple versions of an 
+            item if it is updated. As we only care about the latest, we
+            try to remove any "old" versions of an item that might also be 
+            present within the feed.
+        */
+        $out = [];
+        foreach($items as $item) {
+            foreach($out as $index => $check) {
+                // if the two items have the same ID or any one hash matches, they are two versions of the same item
+                if(
+                    ($item->id && $check->id && $item->id == $check->id) ||
+                    $item->urlTitleHash     == $check->urlTitleHash      ||
+                    $item->urlContentHash   == $check->urlContentHash    ||
+                    $item->titleContentHash == $check->titleContentHash
+                ) {
+                    if(// because newsfeeds are usually order newest-first, the later item should only be used if...
+                        // the later item has an update date and the existing item does not
+                        ($item->updatedDate && !$check->updatedDate) ||
+                        // the later item has an update date newer than the existing item's
+                        ($item->updatedDate && $check->updatedDate && $item->updatedDate->getTimestamp() > $check->updatedDate->getTimestamp()) ||
+                        // neither item has update dates, both have publish dates, and the later item has a newer publish date
+                        (!$item->updatedDate && !$check->updatedDate && $item->publishedDate && $check->publishedDate && $item->publishedDate->getTimestamp() > $check->publishedDate->getTimestamp())
+                    ) {
+                        // if the later item should be used, replace the existing one
+                        $out[$index] = $item;
+                        continue 2;
+                    } else {
+                        // otherwise skip the item
+                        continue 2;
+                    }
+                }
+            }
+            // if there was no match, add the item
+            $out[] = $item;
+        }
+        return $out;
+    }
+
+    protected function matchToDatabase(int $feedID): bool {
+        // first perform deduplication on items
+        $items = $this->deduplicateItems($this->data->items);
+        // get as many of the latest articles in the database as there are in the feed
+        $articles = Data::$db->articleMatchLatest($feedID, sizeof($items));
+        // arrays holding new, edited, and tentatively new items; items may be tentatively new because we perform two passes
+        $new = $tentative = $edited = [];
+        // iterate through the articles and for each determine whether it is existing, edited, or entirely new
+        foreach($items as $index => $i) {
+            foreach($articles as $a) {
+                if(
+                    // the item matches if the GUID matches...
+                    ($i->id && $i->id === $a['guid']) ||
+                    // ... or if any one of the hashes match
+                    $i->urlTitleHash     === $a['url_title_hash']     ||
+                    $i->urlContentHash   === $a['url_content_hash']   ||
+                    $i->titleContentHash === $a['title_content_hash']
+                ) {
+                    if($i->updatedDate && $i->updatedDate->getTimestamp() !== $match['edited_date']) {
+                        // if the item has an edit timestamp and it doesn't match that of the article in the database, the the article has been edited
+                        // we store the item index and database record ID as a key/value pair
+                        $edited[$index] = $a['id'];
+                        break;
+                    } else if($i->urlTitleHash !== $a['url_title_hash'] || $i->urlContentHash !== $a['url_content_hash'] || $i->titleContentHash !== $a['title_content_hash']) {
+                        // if any of the hashes do not match, then the article has been edited
+                        $edited[$index] = $a['id'];
+                        break;
+                    } else {
+                        // otherwise the item is unchanged and we can ignore it
+                        break;
+                    }
+                } else {
+                    // if we don't have a match, add the item to the tentatively new list
+                    $tentative[] = $index;
+                }
+            }
+        }
+        if(sizeof($tentative)) {
+            // if we need to, perform a second pass on the database looking specifically for IDs and hashes of the new items
+            $ids = $hashesUT = $hashesUC = $hashesTC = [];
+            foreach($tentative as $index) {
+                $i = $items[$index];
+                if($i->id) $ids[] = $id->id;
+                $hashesUT[] = $i->urlTitleHash;
+                $hashesUC[] = $i->urlContentHash;
+                $hashesTC[] = $i->titleContentHash;
+            }
+            $articles = Data::$db->articleMatchIds($feedID, $ids, $hashesUT, $hashesUC, $hashesTC);
+            foreach($tentative as $index) {
+                $i = $items[$index];
                 foreach($articles as $a) {
                     if(
                         // the item matches if the GUID matches...
@@ -116,62 +203,19 @@ class Feed {
                             break;
                         }
                     } else {
-                        // if we don't have a match, add the item to the tentatively new list
-                        $tentative[] = $index;
+                        // if we don't have a match, add the item to the definite new list
+                        $new[] = $index;
                     }
                 }
             }
-            if(sizeof($tentative)) {
-                // if we need to, perform a second pass on the database looking specifically for IDs and hashes of the new items
-                $ids = $hashesUT = $hashesUC = $hashesTC = [];
-                foreach($tentative as $index) {
-                    $i = $items[$index];
-                    if($i->id) $ids[] = $id->id;
-                    $hashesUT[] = $i->urlTitleHash;
-                    $hashesUC[] = $i->urlContentHash;
-                    $hashesTC[] = $i->titleContentHash;
-                }
-                $articles = Data::$db->articleMatchIds($feedID, $ids, $hashesUT, $hashesUC, $hashesTC);
-                foreach($tentative as $index) {
-                    $i = $items[$index];
-                    foreach($articles as $a) {
-                        if(
-                            // the item matches if the GUID matches...
-                            ($i->id && $i->id === $a['guid']) ||
-                            // ... or if any one of the hashes match
-                            $i->urlTitleHash     === $a['url_title_hash']     ||
-                            $i->urlContentHash   === $a['url_content_hash']   ||
-                            $i->titleContentHash === $a['title_content_hash']
-                        ) {
-                            if($i->updatedDate && $i->updatedDate->getTimestamp() !== $match['edited_date']) {
-                                // if the item has an edit timestamp and it doesn't match that of the article in the database, the the article has been edited
-                                // we store the item index and database record ID as a key/value pair
-                                $edited[$index] = $a['id'];
-                                break;
-                            } else if($i->urlTitleHash !== $a['url_title_hash'] || $i->urlContentHash !== $a['url_content_hash'] || $i->titleContentHash !== $a['title_content_hash']) {
-                                // if any of the hashes do not match, then the article has been edited
-                                $edited[$index] = $a['id'];
-                                break;
-                            } else {
-                                // otherwise the item is unchanged and we can ignore it
-                                break;
-                            }
-                        } else {
-                            // if we don't have a match, add the item to the definite new list
-                            $new[] = $index;
-                        }
-                    }
-                }
-            }
-            // FIXME: fetch full content when appropriate
-            foreach($new as $index) {
-                $this->newItems[] = $items[$index];
-            }
-            foreach($edited as $index => $id) {
-                $this->changedItems[$id] = $items[$index];
-            }
         }
-        $this->data = $feed;
+        // FIXME: fetch full content when appropriate
+        foreach($new as $index) {
+            $this->newItems[] = $items[$index];
+        }
+        foreach($edited as $index => $id) {
+            $this->changedItems[$id] = $items[$index];
+        }
         return true;
     }
 }
\ No newline at end of file