diff --git a/config/constants.config.php b/config/constants.config.php
index a970072702f..f6220ced6e5 100644
--- a/config/constants.config.php
+++ b/config/constants.config.php
@@ -33,3 +33,6 @@
             ? getenv('VUFIND_CACHE_DIR')
             : (strlen(LOCAL_OVERRIDE_DIR) > 0 ? LOCAL_OVERRIDE_DIR . '/cache' : ''))
     );
+
+// Define database datetime format
+defined('VUFIND_DATABASE_DATETIME_FORMAT') || define('VUFIND_DATABASE_DATETIME_FORMAT', 'Y-m-d H:i:s');
diff --git a/module/VuFind/src/VuFind/Crypt/SecretCalculator.php b/module/VuFind/src/VuFind/Crypt/SecretCalculator.php
index 0dc9fa88f04..344a0d789c0 100644
--- a/module/VuFind/src/VuFind/Crypt/SecretCalculator.php
+++ b/module/VuFind/src/VuFind/Crypt/SecretCalculator.php
@@ -67,7 +67,7 @@ public function getSearchUnsubscribeSecret(SearchEntityInterface $search): strin
         $data = [
             'id' => $search->getId(),
             'user_id' => $user->getId(),
-            'created' => $user->getCreated()->format('Y-m-d H:i:s'),
+            'created' => $user->getCreated()->format(VUFIND_DATABASE_DATETIME_FORMAT),
         ];
         return $this->hmac->generate(array_keys($data), $data);
     }
diff --git a/module/VuFind/src/VuFind/Db/Feature/DateTimeTrait.php b/module/VuFind/src/VuFind/Db/Feature/DateTimeTrait.php
index 9896eee9209..47107020daa 100644
--- a/module/VuFind/src/VuFind/Db/Feature/DateTimeTrait.php
+++ b/module/VuFind/src/VuFind/Db/Feature/DateTimeTrait.php
@@ -53,7 +53,8 @@ trait DateTimeTrait
     protected function getNullableDateTimeFromNonNullable(DateTime $date): ?DateTime
     {
         // Compare strings to avoid trouble with time zones:
-        return $date->format('Y-m-d H:i:s') !== $this->getUnassignedDefaultDateTime()->format('Y-m-d H:i:s')
+        return $date->format(VUFIND_DATABASE_DATETIME_FORMAT)
+            !== $this->getUnassignedDefaultDateTime()->format(VUFIND_DATABASE_DATETIME_FORMAT)
             ? $date
             : null;
     }
diff --git a/module/VuFind/src/VuFind/Db/Service/AccessTokenService.php b/module/VuFind/src/VuFind/Db/Service/AccessTokenService.php
index 09dc6871453..51b01f0abf9 100644
--- a/module/VuFind/src/VuFind/Db/Service/AccessTokenService.php
+++ b/module/VuFind/src/VuFind/Db/Service/AccessTokenService.php
@@ -134,7 +134,7 @@ public function deleteExpired(DateTime $dateLimit, ?int $limit = null): int
         $subQueryBuilder->select('CONCAT(a.id, a.type)')
             ->from(AccessTokenEntityInterface::class, 'a')
             ->where('a.created < :latestCreated')
-            ->setParameter('latestCreated', $dateLimit->format('Y-m-d H:i:s'));
+            ->setParameter('latestCreated', $dateLimit->format(VUFIND_DATABASE_DATETIME_FORMAT));
         if ($limit) {
             $subQueryBuilder->setMaxResults($limit);
         }
diff --git a/module/VuFind/src/VuFind/Db/Service/AuthHashService.php b/module/VuFind/src/VuFind/Db/Service/AuthHashService.php
index 1fdd3bfec41..d5bb0558bf8 100644
--- a/module/VuFind/src/VuFind/Db/Service/AuthHashService.php
+++ b/module/VuFind/src/VuFind/Db/Service/AuthHashService.php
@@ -135,7 +135,7 @@ public function deleteExpired(DateTime $dateLimit, ?int $limit = null): int
         $subQueryBuilder->select('ah.id')
             ->from(AuthHashEntityInterface::class, 'ah')
             ->where('ah.created < :dateLimit')
-            ->setParameter('dateLimit', $dateLimit->format('Y-m-d H:i:s'));
+            ->setParameter('dateLimit', $dateLimit->format(VUFIND_DATABASE_DATETIME_FORMAT));
         if ($limit) {
             $subQueryBuilder->setMaxResults($limit);
         }
diff --git a/module/VuFind/tests/unit-tests/src/VuFindTest/OAuth2/Repository/AbstractTokenRepositoryTestCase.php b/module/VuFind/tests/unit-tests/src/VuFindTest/OAuth2/Repository/AbstractTokenRepositoryTestCase.php
index 598daa9841f..dba8bb30b6c 100644
--- a/module/VuFind/tests/unit-tests/src/VuFindTest/OAuth2/Repository/AbstractTokenRepositoryTestCase.php
+++ b/module/VuFind/tests/unit-tests/src/VuFindTest/OAuth2/Repository/AbstractTokenRepositoryTestCase.php
@@ -356,7 +356,7 @@ protected function createTokenId(): string
      */
     protected function createExpiryDateTime(): \DateTimeImmutable
     {
-        return new \DateTimeImmutable(date('Y-m-d H:i:s', strtotime('now+1hour')));
+        return new \DateTimeImmutable('now+1hour');
     }
 
     /**
diff --git a/module/VuFindApi/src/VuFindApi/Controller/SearchApiController.php b/module/VuFindApi/src/VuFindApi/Controller/SearchApiController.php
index 659ce028428..53fdb8af53d 100644
--- a/module/VuFindApi/src/VuFindApi/Controller/SearchApiController.php
+++ b/module/VuFindApi/src/VuFindApi/Controller/SearchApiController.php
@@ -476,7 +476,7 @@ function (
             $resumptionToken = $this->createResumptionToken($request, $nextCursor, $nextCursorMark);
             $response['resumptionToken'] = [
                 'token' => $resumptionToken->getToken(),
-                'expires' => $resumptionToken->getExpiry()->format('Y-m-d H:i:s'),
+                'expires' => $resumptionToken->getExpiry()->format(VUFIND_DATABASE_DATETIME_FORMAT),
             ];
         }
         return $response;
diff --git a/tests/phpstan-constants.php b/tests/phpstan-constants.php
index 7e90a803c9f..898596b1181 100644
--- a/tests/phpstan-constants.php
+++ b/tests/phpstan-constants.php
@@ -5,4 +5,5 @@
 const DEFAULT_SEARCH_BACKEND = 'Solr';
 const LOCAL_CACHE_DIR = './local';
 const LOCAL_OVERRIDE_DIR = '.';
+const VUFIND_DATABASE_DATETIME_FORMAT = 'Y-m-d H:i:s';