diff --git a/classes/counters.php b/classes/counters.php
index bc4d2d4a3..9699cb97c 100644
--- a/classes/counters.php
+++ b/classes/counters.php
@@ -193,7 +193,7 @@ class Counters {
 			}
 
 			// hide default un-updated timestamp i.e. 1970-01-01 (?) -fox
-			if ((int)date('Y') - (int)date('Y', strtotime($line['last_updated'])) > 2)
+			if ((int)date('Y') - (int)date('Y', strtotime($line['last_updated'] ?? '')) > 2)
 				$last_updated = '';
 
 			$cv = [
diff --git a/classes/digest.php b/classes/digest.php
index 3e943e6dd..a5dbc0945 100644
--- a/classes/digest.php
+++ b/classes/digest.php
@@ -22,7 +22,7 @@ class Digest
 		while ($line = $res->fetch()) {
 
 			if (get_pref(Prefs::DIGEST_ENABLE, $line['id'])) {
-				$preferred_ts = strtotime(get_pref(Prefs::DIGEST_PREFERRED_TIME, $line['id']));
+				$preferred_ts = strtotime(get_pref(Prefs::DIGEST_PREFERRED_TIME, $line['id']) ?? '');
 
 				// try to send digests within 2 hours of preferred time
 				if ($preferred_ts && time() >= $preferred_ts &&
diff --git a/classes/feeditem/atom.php b/classes/feeditem/atom.php
index 59bf403b3..f6c96f959 100755
--- a/classes/feeditem/atom.php
+++ b/classes/feeditem/atom.php
@@ -19,19 +19,19 @@ class FeedItem_Atom extends FeedItem_Common {
 		$updated = $this->elem->getElementsByTagName("updated")->item(0);
 
 		if ($updated) {
-			return strtotime($updated->nodeValue);
+			return strtotime($updated->nodeValue ?? '');
 		}
 
 		$published = $this->elem->getElementsByTagName("published")->item(0);
 
 		if ($published) {
-			return strtotime($published->nodeValue);
+			return strtotime($published->nodeValue ?? '');
 		}
 
 		$date = $this->xpath->query("dc:date", $this->elem)->item(0);
 
 		if ($date) {
-			return strtotime($date->nodeValue);
+			return strtotime($date->nodeValue ?? '');
 		}
 
 		// consistent with strtotime failing to parse
diff --git a/classes/feeditem/rss.php b/classes/feeditem/rss.php
index 132eabff5..e07fd1d06 100755
--- a/classes/feeditem/rss.php
+++ b/classes/feeditem/rss.php
@@ -17,13 +17,13 @@ class FeedItem_RSS extends FeedItem_Common {
 		$pubDate = $this->elem->getElementsByTagName("pubDate")->item(0);
 
 		if ($pubDate) {
-			return strtotime($pubDate->nodeValue);
+			return strtotime($pubDate->nodeValue ?? '');
 		}
 
 		$date = $this->xpath->query("dc:date", $this->elem)->item(0);
 
 		if ($date) {
-			return strtotime($date->nodeValue);
+			return strtotime($date->nodeValue ?? '');
 		}
 
 		// consistent with strtotime failing to parse
diff --git a/classes/handler/public.php b/classes/handler/public.php
index 5c2f2bd02..08b73b87d 100755
--- a/classes/handler/public.php
+++ b/classes/handler/public.php
@@ -128,9 +128,9 @@ class Handler_Public extends Handler {
 				$tpl->setVariable('ARTICLE_CONTENT', $content, true);
 
 				$tpl->setVariable('ARTICLE_UPDATED_ATOM',
-					date('c', strtotime($line["updated"])), true);
+					date('c', strtotime($line["updated"] ?? '')), true);
 				$tpl->setVariable('ARTICLE_UPDATED_RFC822',
-					date(DATE_RFC822, strtotime($line["updated"])), true);
+					date(DATE_RFC822, strtotime($line["updated"] ?? '')), true);
 
 				$tpl->setVariable('ARTICLE_AUTHOR', htmlspecialchars($line['author']), true);
 
@@ -214,7 +214,7 @@ class Handler_Public extends Handler {
 				$article['title'] = $line['title'];
 				$article['excerpt'] = $line["content_preview"];
 				$article['content'] = Sanitizer::sanitize($line["content"], false, $owner_uid, $feed_site_url, null, $line["id"]);
-				$article['updated'] = date('c', strtotime($line["updated"]));
+				$article['updated'] = date('c', strtotime($line["updated"] ?? ''));
 
 				if (!empty($line['note'])) $article['note'] = $line['note'];
 				if (!empty($line['author'])) $article['author'] = $line['author'];
diff --git a/plugins/af_psql_trgm/init.php b/plugins/af_psql_trgm/init.php
index 657b11934..4767e071b 100644
--- a/plugins/af_psql_trgm/init.php
+++ b/plugins/af_psql_trgm/init.php
@@ -122,7 +122,7 @@ class Af_Psql_Trgm extends Plugin {
 
 				print "</div>";
 
-				print "<div style='text-align : right' class='text-muted'>" . TimeHelper::smart_date_time(strtotime($line["updated"])) . "</div>";
+				print "<div style='text-align : right' class='text-muted'>" . TimeHelper::smart_date_time(strtotime($line["updated"] ?? '')) . "</div>";
 
 				print "</li>";
 			}