diff --git a/pyproject.toml b/pyproject.toml
index d375c75..21a393d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -34,7 +34,7 @@ dev = [
     "pylint == 4.0.6",
     "pyrefly==1.1.1",
     "pytest == 9.1.1",
-    "ruff == 0.15.22"
+    "ruff == 0.16.0"
 ]
 
 [build-system]
diff --git a/test/cli_test.py b/test/cli_test.py
index 3ed43fa..6ab7d4a 100644
--- a/test/cli_test.py
+++ b/test/cli_test.py
@@ -16,6 +16,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import unittest
+
 from trackpack import cli
 
 
diff --git a/test/config_test.py b/test/config_test.py
index e20167f..f696fa4 100644
--- a/test/config_test.py
+++ b/test/config_test.py
@@ -17,8 +17,9 @@
 
 import datetime
 import unittest
-from unittest.mock import patch, Mock
-from trackpack import config, cli
+from unittest.mock import patch
+
+from trackpack import cli, config
 
 
 class TestConfig(unittest.TestCase):
@@ -34,8 +35,10 @@ def test_extension_is_stripped_from_archivename(self) -> None:
         cfg.archive_name = "stems.zip"
         self.assertEqual("stems", cfg.archive_name)
 
-    @patch("trackpack.config.date", Mock(today=lambda: datetime.date(2020, 1, 1)))
-    def test_append_date_appends_date_to_archive_name(self) -> None:
+    @patch("trackpack.config.datetime")
+    def test_append_date_appends_date_to_archive_name(self, mock_datetime) -> None:
+        mock_datetime.now.return_value.date.return_value = datetime.date(2020, 1, 1)
+
         cfg = config.Config()
         cfg.archive_name = "xyz"
         cfg.append_date = True
@@ -57,8 +60,10 @@ def test_load_from_yaml(self) -> None:
         cfg.load_from_yaml("name: project-1\narchive_name: proj1\nappend_date: true")
         self.assertTrue(cfg.append_date)
 
-    @patch("trackpack.config.date", Mock(today=lambda: datetime.date(2020, 1, 2)))
-    def test_load_from_cli_args(self) -> None:
+    @patch("trackpack.config.datetime")
+    def test_load_from_cli_args(self, mock_datetime) -> None:
+        mock_datetime.now.return_value.date.return_value = datetime.date(2020, 1, 2)
+
         args = cli.parse_args(["pack", "--archive-name", "proj.zip", "--append-date"])
         cfg = config.Config()
         cfg.archive_name = "should override"
diff --git a/test/trackpack_test.py b/test/trackpack_test.py
index cf43707..3fded61 100644
--- a/test/trackpack_test.py
+++ b/test/trackpack_test.py
@@ -15,10 +15,11 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-import unittest
-from unittest.mock import patch, call
 import os
-from trackpack.trackpacker import TrackPacker, MissingFileException
+import unittest
+from unittest.mock import call, patch
+
+from trackpack.trackpacker import MissingFileException, TrackPacker
 
 
 class TestTrackPack(unittest.TestCase):
diff --git a/trackpack/cli.py b/trackpack/cli.py
index 58def59..60da850 100644
--- a/trackpack/cli.py
+++ b/trackpack/cli.py
@@ -16,6 +16,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import argparse
+
 from trackpack.version import __version__
 
 
diff --git a/trackpack/config.py b/trackpack/config.py
index d0e7020..7b3e565 100644
--- a/trackpack/config.py
+++ b/trackpack/config.py
@@ -15,7 +15,8 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from datetime import date
+from datetime import datetime, timezone
+
 import yaml
 
 
@@ -29,7 +30,8 @@ def __init__(self) -> None:
     @property
     def archive_name(self) -> str:
         if self.append_date:
-            return "-".join((self._archive_name, date.today().strftime("%Y-%m-%d")))
+            today_date = datetime.now(timezone.utc).date()
+            return "-".join((self._archive_name, today_date.strftime("%Y-%m-%d")))
         return self._archive_name
 
     @archive_name.setter
diff --git a/trackpack/trackpacker.py b/trackpack/trackpacker.py
index 9aab950..a7d8c80 100644
--- a/trackpack/trackpacker.py
+++ b/trackpack/trackpacker.py
@@ -57,6 +57,5 @@ def pack_files(self, archive_name: str, files: list[str]):
                 archive.write(file, self.__normalize_stem_name(os.path.basename(file)))
 
     def __normalize_stem_name(self, stem_name: str) -> str:
-        if stem_name.startswith(self.__project_name):
-            stem_name = stem_name[len(self.__project_name) :]
+        stem_name = stem_name.removeprefix(self.__project_name)
         return stem_name.strip().replace(" ", "-")