diff --git a/apps/dav/lib/Files/FileSearchBackend.php b/apps/dav/lib/Files/FileSearchBackend.php
index c819fa6afc684..524f90e6623d1 100644
--- a/apps/dav/lib/Files/FileSearchBackend.php
+++ b/apps/dav/lib/Files/FileSearchBackend.php
@@ -55,7 +55,7 @@
 use SearchDAV\Query\Query;
 
 class FileSearchBackend implements ISearchBackend {
-	const OPERATOR_LIMIT = 100;
+	public const OPERATOR_LIMIT = 100;
 
 	/** @var CachingTree */
 	private $tree;
@@ -432,7 +432,7 @@ private function castValue(SearchPropertyDefinition $property, $value) {
 				if (is_numeric($value)) {
 					return max(0, 0 + $value);
 				}
-				$date = \DateTime::createFromFormat(\DateTimeInterface::ATOM, $value);
+				$date = \DateTime::createFromFormat(\DateTimeInterface::ATOM, (string)$value);
 				return ($date instanceof \DateTime && $date->getTimestamp() !== false) ? $date->getTimestamp() : 0;
 			default:
 				return $value;
diff --git a/apps/files_external/lib/Lib/Storage/FTP.php b/apps/files_external/lib/Lib/Storage/FTP.php
index d424ffe3cdd32..998d147b7c716 100644
--- a/apps/files_external/lib/Lib/Storage/FTP.php
+++ b/apps/files_external/lib/Lib/Storage/FTP.php
@@ -123,7 +123,7 @@ public function filemtime($path) {
 					return $item['type'] === 'cdir';
 				}));
 				if ($currentDir) {
-					$time = \DateTime::createFromFormat('YmdHis', $currentDir['modify']);
+					$time = \DateTime::createFromFormat('YmdHis', $currentDir['modify'] ?? '');
 					if ($time === false) {
 						throw new \Exception("Invalid date format for directory: $currentDir");
 					}
@@ -269,7 +269,7 @@ public function fopen($path, $mode) {
 			case 'wb':
 			case 'wb+':
 				$useExisting = false;
-			// no break
+				// no break
 			case 'a':
 			case 'ab':
 			case 'r+':
diff --git a/apps/sharebymail/lib/ShareByMailProvider.php b/apps/sharebymail/lib/ShareByMailProvider.php
index 01dd3b428d179..af3d14b49bcb6 100644
--- a/apps/sharebymail/lib/ShareByMailProvider.php
+++ b/apps/sharebymail/lib/ShareByMailProvider.php
@@ -1042,8 +1042,8 @@ protected function createShareObject($data) {
 		$share->setShareTime($shareTime);
 		$share->setSharedWith($data['share_with']);
 		$share->setPassword($data['password']);
-		$passwordExpirationTime = \DateTime::createFromFormat('Y-m-d H:i:s', $data['password_expiration_time']);
-		$share->setPasswordExpirationTime($passwordExpirationTime !== false? $passwordExpirationTime : null);
+		$passwordExpirationTime = \DateTime::createFromFormat('Y-m-d H:i:s', $data['password_expiration_time'] ?? '');
+		$share->setPasswordExpirationTime($passwordExpirationTime !== false ? $passwordExpirationTime : null);
 		$share->setLabel($data['label']);
 		$share->setSendPasswordByTalk((bool)$data['password_by_talk']);
 		$share->setHideDownload((bool)$data['hide_download']);
@@ -1140,7 +1140,6 @@ public function userDeletedFromGroup($uid, $gid) {
 	 * @throws ShareNotFound
 	 */
 	protected function getRawShare($id) {
-
 		// Now fetch the inserted share and create a complete share object
 		$qb = $this->dbConnection->getQueryBuilder();
 		$qb->select('*')
diff --git a/apps/workflowengine/lib/Check/RequestTime.php b/apps/workflowengine/lib/Check/RequestTime.php
index b7a2f72545168..be28f8ead1597 100644
--- a/apps/workflowengine/lib/Check/RequestTime.php
+++ b/apps/workflowengine/lib/Check/RequestTime.php
@@ -109,12 +109,12 @@ public function validateCheck($operator, $value) {
 		}
 
 		$values = json_decode($value, true);
-		$time1 = \DateTime::createFromFormat('H:i e', $values[0]);
+		$time1 = \DateTime::createFromFormat('H:i e', (string)$values[0]);
 		if ($time1 === false) {
 			throw new \UnexpectedValueException($this->l->t('The given start time is invalid'), 3);
 		}
 
-		$time2 = \DateTime::createFromFormat('H:i e', $values[1]);
+		$time2 = \DateTime::createFromFormat('H:i e', (string)$values[1]);
 		if ($time2 === false) {
 			throw new \UnexpectedValueException($this->l->t('The given end time is invalid'), 4);
 		}