diff --git a/apps/dav/lib/Files/FileSearchBackend.php b/apps/dav/lib/Files/FileSearchBackend.php
index 45e911db182..36f68edaf90 100644
--- a/apps/dav/lib/Files/FileSearchBackend.php
+++ b/apps/dav/lib/Files/FileSearchBackend.php
@@ -376,7 +376,7 @@ class FileSearchBackend implements ISearchBackend {
 				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 d424ffe3cdd..998d147b7c7 100644
--- a/apps/files_external/lib/Lib/Storage/FTP.php
+++ b/apps/files_external/lib/Lib/Storage/FTP.php
@@ -123,7 +123,7 @@ class FTP extends Common {
 					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 @@ class FTP extends Common {
 			case 'wb':
 			case 'wb+':
 				$useExisting = false;
-			// no break
+				// no break
 			case 'a':
 			case 'ab':
 			case 'r+':
diff --git a/apps/sharebymail/lib/ShareByMailProvider.php b/apps/sharebymail/lib/ShareByMailProvider.php
index debc9300f1b..3cfa452e412 100644
--- a/apps/sharebymail/lib/ShareByMailProvider.php
+++ b/apps/sharebymail/lib/ShareByMailProvider.php
@@ -1099,7 +1099,6 @@ class ShareByMailProvider implements IShareProvider {
 	 * @throws ShareNotFound
 	 */
 	protected function getRawShare($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 b7a2f725451..be28f8ead15 100644
--- a/apps/workflowengine/lib/Check/RequestTime.php
+++ b/apps/workflowengine/lib/Check/RequestTime.php
@@ -109,12 +109,12 @@ class RequestTime implements ICheck {
 		}
 
 		$values = json_decode($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);
 		}