diff --git a/.github/workflows/python-tests.yml b/.github/workflows/python-tests.yml
index f623ae2274..e7c3d03578 100644
--- a/.github/workflows/python-tests.yml
+++ b/.github/workflows/python-tests.yml
@@ -854,6 +854,11 @@ jobs:
       - name: Verify native Windows test Python discovery
         run: node --no-warnings --experimental-strip-types --test tests/control_plane_ts/test_python_runtime.test.ts
 
+      - name: Qualify named report timezones on Windows
+        run: >-
+          python -m pytest -q tests/capabilities/test_periodic_report_cadence.py
+          tests/capabilities/test_periodic_report_machine_defaults.py
+
       - name: Qualify captured research fixture integrity on Windows
         env:
           PYTHONUTF8: "0"
diff --git a/pyproject.toml b/pyproject.toml
index ac23ce6060..9f99527e47 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -11,9 +11,10 @@ requires-python = ">=3.11"
 license = "Apache-2.0"
 license-files = ["LICENSE", "NOTICE", "LICENSE-MIT"]
 authors = [{ name = "LoopX contributors" }]
-# No Python runtime dependencies, but the TypeScript control plane needs a
-# system Node.js >= 22.22.3 (MINIMUM_NODE_VERSION); pip cannot install it.
-dependencies = []
+# Windows does not supply the IANA database used by zoneinfo for schedules.
+# The TypeScript control plane also needs system Node.js >= 22.22.3
+# (MINIMUM_NODE_VERSION); pip cannot install it.
+dependencies = ["tzdata; sys_platform == 'win32'"]
 
 [project.urls]
 Homepage = "https://loopx-project.github.io/loopx/"