Fix history graphs with mysql/mariadb (#36769)

homeassistant/components/history/__init__.py

@@ -12,11 +12,7 @@ import voluptuous as vol
 
 from homeassistant.components import recorder
 from homeassistant.components.http import HomeAssistantView
-from homeassistant.components.recorder.models import (
-    DB_TIMEZONE,
-    States,
-    process_timestamp,
-)
+from homeassistant.components.recorder.models import States, process_timestamp
 from homeassistant.components.recorder.util import execute, session_scope
 from homeassistant.const import (
     ATTR_HIDDEN,
@@ -355,7 +351,9 @@ def _sorted_states_to_json(
             ent_results.append(
                 {
                     STATE_KEY: db_state.state,
-                    LAST_CHANGED_KEY: f"{str(_process_timestamp(db_state.last_changed)).replace(' ','T').split('.')[0]}{DB_TIMEZONE}",
+                    LAST_CHANGED_KEY: _process_timestamp(
+                        db_state.last_changed
+                    ).isoformat(),
                 }
             )
             prev_state = db_state

tests/components/history/test_init.py

@@ -223,11 +223,8 @@ class TestComponentHistory(unittest.TestCase):
         # will happen with encoding a native state
         input_state = states["media_player.test"][1]
         orig_last_changed = json.dumps(
-            process_timestamp(input_state.last_changed.replace(microsecond=0)),
-            cls=JSONEncoder,
+            process_timestamp(input_state.last_changed), cls=JSONEncoder,
         ).replace('"', "")
-        if orig_last_changed.endswith("+00:00"):
-            orig_last_changed = f"{orig_last_changed[:-6]}{recorder.models.DB_TIMEZONE}"
         orig_state = input_state.state
         states["media_player.test"][1] = {
             "last_changed": orig_last_changed,