Avoid a naive datetime.now() in huawei_lte (#178605)

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

homeassistant/components/huawei_lte/sensor.py

@@ -28,6 +28,7 @@ from homeassistant.core import HomeAssistant
 from homeassistant.helpers.entity import Entity
 from homeassistant.helpers.entity_platform import AddConfigEntryEntitiesCallback
 from homeassistant.helpers.typing import StateType
+from homeassistant.util import dt as dt_util
 
 from . import HuaweiLteConfigEntry, Router
 from .const import (
@@ -76,11 +77,10 @@ def format_last_reset_elapsed_seconds(value: str | None) -> datetime | None:
     if value is None:
         return None
     try:
-        last_reset = datetime.now() - timedelta(seconds=int(value))  # pylint: disable=home-assistant-enforce-naive-now
-        last_reset.replace(microsecond=0)
+        elapsed = timedelta(seconds=int(value))
     except ValueError:
         return None
-    return last_reset
+    return (dt_util.utcnow() - elapsed).replace(microsecond=0)
 
 
 def format_ipv6(value: StateType) -> tuple[StateType, str | None]:

tests/components/huawei_lte/test_sensor.py

@@ -1,5 +1,8 @@
 """Huawei LTE sensor tests."""
 
+from datetime import timedelta
+
+from freezegun.api import FrozenDateTimeFactory
 import pytest
 
 from homeassistant.components.huawei_lte import sensor
@@ -7,6 +10,7 @@ from homeassistant.const import (
     SIGNAL_STRENGTH_DECIBELS,
     SIGNAL_STRENGTH_DECIBELS_MILLIWATT,
 )
+from homeassistant.util import dt as dt_util
 
 
 @pytest.mark.parametrize(
@@ -22,3 +26,31 @@ from homeassistant.const import (
 def test_format_default(value, expected) -> None:
     """Test that default formatter copes with expected values."""
     assert sensor.format_default(value) == expected
+
+
+@pytest.mark.parametrize(
+    ("value", "expected_elapsed"),
+    [
+        ("0", timedelta(0)),
+        ("90", timedelta(seconds=90)),
+        ("86400", timedelta(days=1)),
+    ],
+)
+def test_format_last_reset_elapsed_seconds(
+    freezer: FrozenDateTimeFactory, value: str, expected_elapsed: timedelta
+) -> None:
+    """Test elapsed seconds are turned into an aware, truncated reset time."""
+    freezer.move_to("2026-01-02T03:04:05.678901+00:00")
+
+    result = sensor.format_last_reset_elapsed_seconds(value)
+
+    assert result is not None
+    assert result.tzinfo is not None
+    assert result.microsecond == 0
+    assert result == dt_util.utcnow().replace(microsecond=0) - expected_elapsed
+
+
+@pytest.mark.parametrize("value", [None, "", "not a number"])
+def test_format_last_reset_elapsed_seconds_invalid(value: str | None) -> None:
+    """Test values that cannot be converted are ignored."""
+    assert sensor.format_last_reset_elapsed_seconds(value) is None