diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index 33bc7d1..71dcaf9 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -20,3 +20,5 @@ jobs:
       run: pip install -e .[test]
     - name: Run tests
       run: python -m pytest
+      env:
+        TZ: AUS Eastern Standard Time
diff --git a/tests/test_renamer.py b/tests/test_renamer.py
index 85a03bf..5e10a29 100644
--- a/tests/test_renamer.py
+++ b/tests/test_renamer.py
@@ -1,3 +1,5 @@
+import os
+import time
 from shroudstone.renamer import Replay, new_name_for
 from tests.conftest import ReplayCase
 
@@ -6,6 +8,19 @@
     "{time:%Y-%m-%d %H.%M} {duration} {players_with_factions} - {map_name}.SGReplay"
 )
 
+# Since we have to resort to getting replay timestamps from the *local time*
+# in the filename, shroudstone's behaviour is dependent upon the system timezone.
+# Thus for the purposes of a consistent test suite we override TZ.
+if os.environ.get("TZ") not in ("Australia/Melbourne", "AUS Eastern Standard Time"):
+    if hasattr(time, "tzset"):
+        os.environ["TZ"] = "Australia/Melbourne"
+        time.tzset()
+    else:
+        raise RuntimeError(
+            "Incorrect timezone set and tzset is not available, "
+            "so tests would fail. Please set TZ=Australia/Melbourne to run the tests on Windows."
+        )
+
 
 def test_replay_renaming(replay_case: ReplayCase, request):
     replay = Replay.from_path(replay_case.replay_file)