diff --git a/fdroidserver/scanner.py b/fdroidserver/scanner.py
index 81f4ce70..797d694e 100644
--- a/fdroidserver/scanner.py
+++ b/fdroidserver/scanner.py
@@ -114,7 +114,7 @@ def get_embedded_classes(apkfile, depth=0):
 
 def _datetime_now():
     """Get datetime.now(), using this funciton allows mocking it for testing."""
-    return datetime.now().astimezone()
+    return datetime.utcnow()
 
 
 def _scanner_cachedir():
diff --git a/tests/scanner.TestCase b/tests/scanner.TestCase
index c3c70ffe..a5ad3779 100755
--- a/tests/scanner.TestCase
+++ b/tests/scanner.TestCase
@@ -508,13 +508,13 @@ class Test_SignatureDataController(unittest.TestCase):
     # check_last_updated
     def test_check_last_updated_ok(self):
         sdc = fdroidserver.scanner.SignatureDataController('nnn', 'fff.yml', 'https://example.com/test.json')
-        sdc.data['last_updated'] = datetime.now().astimezone().isoformat()
+        sdc.data['last_updated'] = datetime.utcnow().isoformat()
         sdc.check_last_updated()
 
     def test_check_last_updated_exception_cache_outdated(self):
         sdc = fdroidserver.scanner.SignatureDataController('nnn', 'fff.yml', 'https://example.com/test.json')
         sdc.cache_duration = timedelta(days=7)
-        sdc.data['last_updated'] = (datetime.now().astimezone() - timedelta(days=30)).isoformat()
+        sdc.data['last_updated'] = (datetime.utcnow() - timedelta(days=30)).isoformat()
         with self.assertRaises(fdroidserver.scanner.SignatureDataOutdatedException):
             sdc.check_last_updated()