Use UTC datetimes internally (#84)

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/composite/device_tracker.py

@@ -378,8 +378,13 @@ async def _restore_state(self) -> None:
             last_seen = dt_util.parse_datetime(
                 self._attr_extra_state_attributes[ATTR_LAST_SEEN]
             )
-            self._attr_extra_state_attributes[ATTR_LAST_SEEN] = last_seen
-            self._prev_seen = last_seen
+            if last_seen is None:
+                self._attr_extra_state_attributes[ATTR_LAST_SEEN] = None
+            else:
+                self._attr_extra_state_attributes[ATTR_LAST_SEEN] = dt_util.as_local(
+                    last_seen
+                )
+                self._prev_seen = dt_util.as_utc(last_seen)
         if self.source_type in _SOURCE_TYPE_NON_GPS and (
             self.latitude is None or self.longitude is None
         ):
@@ -410,21 +415,21 @@ async def _entity_updated(  # noqa: C901
         # attributes defined by _LAST_SEEN_ATTRS, as a datetime.
 
         def get_last_seen() -> datetime | None:
-            """Get last_seen from one of the possible attributes."""
+            """Get last_seen (in UTC) from one of the possible attributes."""
             if (raw_last_seen := new_attrs.get(_LAST_SEEN_ATTRS)) is None:
                 return None
             if isinstance(raw_last_seen, datetime):
-                return raw_last_seen
+                return dt_util.as_utc(raw_last_seen)
             with suppress(TypeError, ValueError):
                 return dt_util.utc_from_timestamp(float(raw_last_seen))
             with suppress(TypeError):
-                return dt_util.parse_datetime(raw_last_seen)
+                if (parsed_last_seen := dt_util.parse_datetime(raw_last_seen)) is None:
+                    return None
+                return dt_util.as_utc(parsed_last_seen)
             return None
 
-        # Make sure last_seen is timezone aware in local timezone.
-        # Note that dt_util.as_local assumes naive datetime is in local timezone.
         # Use last_updated from the new state object if no valid "last seen" was found.
-        last_seen = dt_util.as_local(get_last_seen() or new_state.last_updated)
+        last_seen = get_last_seen() or new_state.last_updated
 
         old_last_seen = entity.seen
         if old_last_seen and last_seen < old_last_seen:
@@ -549,8 +554,8 @@ def get_last_seen() -> datetime | None:
                 "last_seen not newer than previous update (%s) <= (%s)",
                 self.entity_id,
                 entity_id,
-                last_seen,
-                self._prev_seen,
+                dt_util.as_local(last_seen),
+                dt_util.as_local(self._prev_seen),
             )
             return
 
@@ -563,7 +568,7 @@ def get_last_seen() -> datetime | None:
                 if _entity.source_type
             ),
             ATTR_LAST_ENTITY_ID: entity_id,
-            ATTR_LAST_SEEN: _nearest_second(last_seen),
+            ATTR_LAST_SEEN: dt_util.as_local(_nearest_second(last_seen)),
         }
         if charging is not None:
             attrs[ATTR_BATTERY_CHARGING] = charging
@@ -617,6 +622,9 @@ def _set_state(
             assert attributes
             last_ent = cast(str, attributes[ATTR_LAST_ENTITY_ID])
             last_seen = cast(datetime, attributes[ATTR_LAST_SEEN])
+            # It's ok that last_seen is in local tz and self._prev_seen is in UTC.
+            # last_seen's value will automatically be converted to UTC during the
+            # subtraction operation.
             seconds = (last_seen - self._prev_seen).total_seconds()
             min_seconds = MIN_SPEED_SECONDS
             if last_ent != prev_ent:

custom_components/composite/manifest.json

@@ -4,9 +4,9 @@
   "codeowners": ["@pnbruckner"],
   "config_flow": true,
   "dependencies": ["file_upload"],
-  "documentation": "https://github.com/pnbruckner/ha-composite-tracker/blob/3.4.4/README.md",
+  "documentation": "https://github.com/pnbruckner/ha-composite-tracker/blob/3.4.5b0/README.md",
   "iot_class": "local_polling",
   "issue_tracker": "https://github.com/pnbruckner/ha-composite-tracker/issues",
   "requirements": ["filetype==1.2.0"],
-  "version": "3.4.4"
+  "version": "3.4.5b0"
 }