Use UTC datetimes internally (#73)

Python datetime object comparisons and math don't work as expected
when the objects are aware and have the same tzinfo attribute.
Basically, the fold attribute is ignored in this case, which can lead to
wrong results. Avoid this problem by using aware times in UTC internally.
Only use local time zone for user visible attributes.

custom_components/illuminance/sensor.py

@@ -351,7 +351,7 @@ async def async_update(self) -> None:
             return
 
         try:
-            value = self._calculate_illuminance(dt_util.now().replace(microsecond=0))
+            value = self._calculate_illuminance(dt_util.utcnow().replace(microsecond=0))
         except AbortUpdate:
             return
 
@@ -492,11 +492,13 @@ def _calculate_illuminance(self, now: datetime) -> Num:
     def _astral_event(self, event: str, date_or_dt: date | datetime) -> Any:
         """Get astral event."""
         loc, elev = cast(tuple[Location, Elevation], self.hass.data[DOMAIN])
-        return getattr(loc, event)(date_or_dt, observer_elevation=elev)
+        if event == "solar_elevation":
+            return getattr(loc, event)(date_or_dt, observer_elevation=elev)
+        return getattr(loc, event)(date_or_dt, local=False, observer_elevation=elev)
 
     def _sun_factor(self, now: datetime) -> Num:
         """Calculate sun factor."""
-        now_date = now.date()
+        now_date = dt_util.as_local(now).date()
 
         if self._sun_data and self._sun_data[0] == now_date:
             (sunrise_begin, sunrise_end, sunset_begin, sunset_end) = self._sun_data[1]