@@ -4,8 +4,10 @@
 
 from datetime import datetime
 from enum import Enum
+from typing import TYPE_CHECKING
 
 from ...feature import Feature
+from ...interfaces.time import Time
 from ..smartmodule import Module, SmartModule
 
 
@@ -76,6 +78,17 @@ def alert(self) -> bool:
         """Return true if alarm is active."""
         return self._device.sys_info["in_alarm"]
 
+    @property
+    def _time_module(self) -> Time:
+        """Return time module from the parent for timestamp calculation."""
+        parent = self._device.parent
+        if TYPE_CHECKING:
+            from ..smartdevice import SmartDevice
+
+            assert isinstance(parent, SmartDevice)
+
+        return parent.modules[Module.Time]
+
     @property
     def alert_timestamp(self) -> datetime | None:
         """Return timestamp of the last leak trigger."""
@@ -84,5 +97,5 @@ def alert_timestamp(self) -> datetime | None:
             return None
 
         ts = self._device.sys_info["trigger_timestamp"]
-        tz = self._device.modules[Module.Time].timezone
+        tz = self._time_module.timezone
         return datetime.fromtimestamp(ts, tz=tz)
@@ -5,13 +5,20 @@
 
 from kasa.smart.modules import WaterleakSensor
 
+from ...conftest import get_device_for_fixture_protocol
 from ...device_fixtures import parametrize
 
 waterleak = parametrize(
     "has waterleak", component_filter="sensor_alarm", protocol_filter={"SMART.CHILD"}
 )
 
 
+@pytest.fixture
+async def parent(request):
+    """Get a dummy parent for tz tests."""
+    return await get_device_for_fixture_protocol("H100(EU)_1.0_1.5.5.json", "SMART")
+
+
 @waterleak
 @pytest.mark.parametrize(
     ("feature", "prop_name", "type"),
@@ -21,8 +28,9 @@
         ("water_leak", "status", Enum),
     ],
 )
-async def test_waterleak_properties(dev, feature, prop_name, type):
+async def test_waterleak_properties(dev, parent, feature, prop_name, type):
     """Test that features are registered and work as expected."""
+    dev._parent = parent
     waterleak: WaterleakSensor = dev.modules["WaterleakSensor"]
 
     prop = getattr(waterleak, prop_name)
@@ -34,12 +42,16 @@ async def test_waterleak_properties(dev, feature, prop_name, type):
 
 
 @waterleak
-async def test_waterleak_features(dev):
+async def test_waterleak_features(dev, parent):
     """Test waterleak features."""
+    dev._parent = parent
     waterleak: WaterleakSensor = dev.modules["WaterleakSensor"]
 
     assert "water_leak" in dev.features
     assert dev.features["water_leak"].value == waterleak.status
 
     assert "water_alert" in dev.features
     assert dev.features["water_alert"].value == waterleak.alert
+
+    assert "water_alert_timestamp" in dev.features
+    assert dev.features["water_alert_timestamp"].value == waterleak.alert_timestamp