diff --git a/picard/script/serializer.py b/picard/script/serializer.py
index 4f5d85544a..65763bfb97 100644
--- a/picard/script/serializer.py
+++ b/picard/script/serializer.py
@@ -3,7 +3,7 @@
 # Picard, the next-generation MusicBrainz tagger
 #
 # Copyright (C) 2021, 2023 Bob Swift
-# Copyright (C) 2021-2023 Philipp Wolfer
+# Copyright (C) 2021-2024 Philipp Wolfer
 # Copyright (C) 2021-2024 Laurent Monin
 #
 # This program is free software; you can redistribute it and/or
@@ -152,7 +152,7 @@ def make_last_updated():
         Returns:
             str: Last updated string from current date and time
         """
-        return datetime.datetime.utcnow().strftime('%Y-%m-%d %H:%M:%S UTC')
+        return datetime.datetime.now(datetime.timezone.utc).strftime('%Y-%m-%d %H:%M:%S UTC')
 
     def update_last_updated(self):
         """Update the last updated attribute to the current UTC date and time.
diff --git a/setup.py b/setup.py
index 5226e60e01..66897e148f 100644
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,7 @@
 # Copyright (C) 2006-2008, 2011-2014, 2017 Lukáš Lalinský
 # Copyright (C) 2007 Santiago M. Mola
 # Copyright (C) 2008 Robert Kaye
-# Copyright (C) 2008-2009, 2018-2022 Philipp Wolfer
+# Copyright (C) 2008-2009, 2018-2024 Philipp Wolfer
 # Copyright (C) 2009 Carlin Mangar
 # Copyright (C) 2011-2012, 2014, 2016-2018 Wieland Hoffmann
 # Copyright (C) 2011-2014 Michael Wiencek
@@ -716,7 +716,7 @@ def patch_version(self, filename):
         regex = re.compile(r'^PICARD_BUILD_VERSION_STR\s*=.*$', re.MULTILINE)
         with open(filename, 'r+b') as f:
             source = (f.read()).decode()
-            build = self.platform + '.' + datetime.datetime.utcnow().strftime('%Y%m%d%H%M%S')
+            build = self.platform + '.' + datetime.datetime.now(datetime.timezone.utc).strftime('%Y%m%d%H%M%S')
             patched_source = regex.sub('PICARD_BUILD_VERSION_STR = "%s"' % build, source).encode()
             f.seek(0)
             f.write(patched_source)
diff --git a/test/test_script_serializer.py b/test/test_script_serializer.py
index 9e5c286529..943c06bf32 100644
--- a/test/test_script_serializer.py
+++ b/test/test_script_serializer.py
@@ -3,7 +3,7 @@
 # Picard, the next-generation MusicBrainz tagger
 #
 # Copyright (C) 2021 Bob Swift
-# Copyright (C) 2021 Philipp Wolfer
+# Copyright (C) 2021, 2024 Philipp Wolfer
 #
 # This program is free software; you can redistribute it and/or
 # modify it under the terms of the GNU General Public License
@@ -21,6 +21,7 @@
 
 
 import datetime
+from unittest.mock import patch
 
 import yaml
 
@@ -33,26 +34,17 @@
 )
 
 
-class _DateTime(datetime.datetime):
+class MockDateTime(datetime.datetime):
     @classmethod
-    def utcnow(cls):
-        return cls(year=2020, month=1, day=2, hour=12, minute=34, second=56, microsecond=789, tzinfo=None)
+    def now(cls, tz=None):
+        if tz == datetime.timezone.utc:
+            return cls(year=2020, month=1, day=2, hour=12, minute=34, second=56, microsecond=789, tzinfo=None)
+        else:
+            raise Exception("Unexpected parameter tz=%r" % tz)
 
 
 class PicardScriptTest(PicardTestCase):
 
-    original_datetime = datetime.datetime
-
-    def setUp(self):
-        super().setUp()
-        # Save original datetime object and substitute one returning
-        # a fixed utcnow() value for testing.
-        datetime.datetime = _DateTime
-
-    def tearDown(self):
-        # Restore original datetime object
-        datetime.datetime = self.original_datetime
-
     def assertYamlEquals(self, yaml_str, obj, msg=None):
         self.assertEqual(obj, yaml.safe_load(yaml_str), msg)
 
@@ -88,6 +80,7 @@ def test_script_object_3(self):
         self.assertEqual(test_script.last_updated, '2021-04-26')
         self.assertEqual(test_script['last_updated'], '2021-04-26')
 
+    @patch('datetime.datetime', MockDateTime)
     def test_script_object_4(self):
         # Check updating values that modify `last_updated`.
         test_script = PicardScript(title='Script 1', script='Script text', id='12345', last_updated='2021-04-26')
@@ -97,6 +90,7 @@ def test_script_object_4(self):
         self.assertEqual(test_script.last_updated, '2020-01-02 12:34:56 UTC')
         self.assertEqual(test_script['last_updated'], '2020-01-02 12:34:56 UTC')
 
+    @patch('datetime.datetime', MockDateTime)
     def test_script_object_5(self):
         # Check updating values from dict that modify `last_updated`.
         test_script = PicardScript(title='Script 1', script='Script text', id='12345', last_updated='2021-04-26')