diff --git a/homeassistant/components/teslemetry/calendar.py b/homeassistant/components/teslemetry/calendar.py
index a6d4077168f4..87bb2ddf9932 100644
--- a/homeassistant/components/teslemetry/calendar.py
+++ b/homeassistant/components/teslemetry/calendar.py
@@ -1,6 +1,6 @@
 """Calendar platform for Teslemetry integration."""
 
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, tzinfo
 from typing import Any, override
 
 from homeassistant.components.calendar import CalendarEntity, CalendarEvent
@@ -111,6 +111,8 @@ def _build_event(
 class TeslemetryTariffSchedule(TeslemetryEnergyInfoEntity, CalendarEntity):
     """Energy Site Tariff Schedule Calendar."""
 
+    _time_zone: tzinfo
+
     def __init__(
         self,
         data: Any,
@@ -122,11 +124,20 @@ class TeslemetryTariffSchedule(TeslemetryEnergyInfoEntity, CalendarEntity):
         self.charges: dict[str, dict[str, Any]] = {}
         super().__init__(data, key_base)
 
+    @override
+    async def async_added_to_hass(self) -> None:
+        """Resolve the site timezone the tariff is defined in."""
+        name = self.coordinator.data.get("installation_time_zone")
+        self._time_zone = (
+            name and await dt_util.async_get_time_zone(name)
+        ) or dt_util.get_default_time_zone()
+        await super().async_added_to_hass()
+
     @property
     @override
     def event(self) -> CalendarEvent | None:
         """Return the current active tariff event."""
-        now = dt_util.now()
+        now = dt_util.now(self._time_zone)
         current_season_name = self._get_current_season(now)
 
         if not current_season_name or not self.seasons.get(current_season_name):
@@ -173,12 +184,14 @@ class TeslemetryTariffSchedule(TeslemetryEnergyInfoEntity, CalendarEntity):
         """Return calendar events (tariff periods) within a datetime range."""
         events: list[CalendarEvent] = []
 
-        start_date = dt_util.as_local(start_date)
-        end_date = dt_util.as_local(end_date)
+        start_date = start_date.astimezone(self._time_zone)
+        end_date = end_date.astimezone(self._time_zone)
 
         # Start one day earlier to catch TOU periods that cross midnight
         # from the previous evening into the query range.
-        current_day = dt_util.start_of_local_day(start_date) - timedelta(days=1)
+        current_day = start_date.replace(
+            hour=0, minute=0, second=0, microsecond=0
+        ) - timedelta(days=1)
         while current_day < end_date:
             season_name = self._get_current_season(current_day)
             if not season_name or not self.seasons.get(season_name):
@@ -215,7 +228,7 @@ class TeslemetryTariffSchedule(TeslemetryEnergyInfoEntity, CalendarEntity):
 
     def _get_current_season(self, date_to_check: datetime) -> str | None:
         """Determine the active season for a given date."""
-        local_date = dt_util.as_local(date_to_check)
+        local_date = date_to_check.astimezone(self._time_zone)
         year = local_date.year
 
         for season_name, season_data in self.seasons.items():
diff --git a/tests/components/teslemetry/snapshots/test_calendar.ambr b/tests/components/teslemetry/snapshots/test_calendar.ambr
index b9f871c00216..93a96d9c9f20 100644
--- a/tests/components/teslemetry/snapshots/test_calendar.ambr
+++ b/tests/components/teslemetry/snapshots/test_calendar.ambr
@@ -45,11 +45,11 @@
         Period: Off peak
         Price: 0.20/kWh
       ''',
-      <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 16:00:00',
+      <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2023-12-31 22:00:00',
       <EntityStateAttribute.FRIENDLY_NAME: 'friendly_name'>: 'Energy Site Buy tariff',
       <CalendarEntityStateAttribute.LOCATION: 'location'>: '',
       <CalendarEntityStateAttribute.MESSAGE: 'message'>: 'Off peak: 0.20/kWh',
-      <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 21:00:00',
+      <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 03:00:00',
     }),
     'context': <ANY>,
     'entity_id': 'calendar.energy_site_buy_tariff',
@@ -105,11 +105,11 @@
         Period: Off peak
         Price: 0.08/kWh
       ''',
-      <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 16:00:00',
+      <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2023-12-31 22:00:00',
       <EntityStateAttribute.FRIENDLY_NAME: 'friendly_name'>: 'Energy Site Sell tariff',
       <CalendarEntityStateAttribute.LOCATION: 'location'>: '',
       <CalendarEntityStateAttribute.MESSAGE: 'message'>: 'Off peak: 0.08/kWh',
-      <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 21:00:00',
+      <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 03:00:00',
     }),
     'context': <ANY>,
     'entity_id': 'calendar.energy_site_sell_tariff',
@@ -127,35 +127,25 @@
       Period: Off peak
       Price: 0.20/kWh
     ''',
-    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 16:00:00',
+    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2023-12-31 22:00:00',
     <EntityStateAttribute.FRIENDLY_NAME: 'friendly_name'>: 'Energy Site Buy tariff',
     <CalendarEntityStateAttribute.LOCATION: 'location'>: '',
     <CalendarEntityStateAttribute.MESSAGE: 'message'>: 'Off peak: 0.20/kWh',
-    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 21:00:00',
+    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 03:00:00',
   })
 # ---
 # name: test_calendar_events[time_tuple0-calendar.energy_site_buy_tariff][events]
   dict({
     'calendar.energy_site_buy_tariff': dict({
       'events': list([
-        dict({
-          'description': '''
-            Season: Summer
-            Period: On peak
-            Price: 0.22/kWh
-          ''',
-          'end': '2023-12-31T21:00:00-08:00',
-          'start': '2023-12-31T16:00:00-08:00',
-          'summary': 'On peak: 0.22/kWh',
-        }),
         dict({
           'description': '''
             Season: Summer
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-01T16:00:00-08:00',
-          'start': '2023-12-31T21:00:00-08:00',
+          'end': '2024-01-01T16:00:00+10:00',
+          'start': '2023-12-31T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -164,8 +154,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-01T21:00:00-08:00',
-          'start': '2024-01-01T16:00:00-08:00',
+          'end': '2024-01-01T21:00:00+10:00',
+          'start': '2024-01-01T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -174,8 +164,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-02T16:00:00-08:00',
-          'start': '2024-01-01T21:00:00-08:00',
+          'end': '2024-01-02T16:00:00+10:00',
+          'start': '2024-01-01T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -184,8 +174,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-02T21:00:00-08:00',
-          'start': '2024-01-02T16:00:00-08:00',
+          'end': '2024-01-02T21:00:00+10:00',
+          'start': '2024-01-02T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -194,8 +184,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-03T16:00:00-08:00',
-          'start': '2024-01-02T21:00:00-08:00',
+          'end': '2024-01-03T16:00:00+10:00',
+          'start': '2024-01-02T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -204,8 +194,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-03T21:00:00-08:00',
-          'start': '2024-01-03T16:00:00-08:00',
+          'end': '2024-01-03T21:00:00+10:00',
+          'start': '2024-01-03T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -214,8 +204,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-04T16:00:00-08:00',
-          'start': '2024-01-03T21:00:00-08:00',
+          'end': '2024-01-04T16:00:00+10:00',
+          'start': '2024-01-03T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -224,8 +214,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-04T21:00:00-08:00',
-          'start': '2024-01-04T16:00:00-08:00',
+          'end': '2024-01-04T21:00:00+10:00',
+          'start': '2024-01-04T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -234,8 +224,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-05T16:00:00-08:00',
-          'start': '2024-01-04T21:00:00-08:00',
+          'end': '2024-01-05T16:00:00+10:00',
+          'start': '2024-01-04T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -244,8 +234,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-05T21:00:00-08:00',
-          'start': '2024-01-05T16:00:00-08:00',
+          'end': '2024-01-05T21:00:00+10:00',
+          'start': '2024-01-05T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -254,8 +244,28 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-06T16:00:00-08:00',
-          'start': '2024-01-05T21:00:00-08:00',
+          'end': '2024-01-06T16:00:00+10:00',
+          'start': '2024-01-05T21:00:00+10:00',
+          'summary': 'Off peak: 0.20/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: On peak
+            Price: 0.22/kWh
+          ''',
+          'end': '2024-01-06T21:00:00+10:00',
+          'start': '2024-01-06T16:00:00+10:00',
+          'summary': 'On peak: 0.22/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: Off peak
+            Price: 0.20/kWh
+          ''',
+          'end': '2024-01-07T16:00:00+10:00',
+          'start': '2024-01-06T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
       ]),
@@ -270,35 +280,25 @@
       Period: Off peak
       Price: 0.08/kWh
     ''',
-    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 16:00:00',
+    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2023-12-31 22:00:00',
     <EntityStateAttribute.FRIENDLY_NAME: 'friendly_name'>: 'Energy Site Sell tariff',
     <CalendarEntityStateAttribute.LOCATION: 'location'>: '',
     <CalendarEntityStateAttribute.MESSAGE: 'message'>: 'Off peak: 0.08/kWh',
-    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 21:00:00',
+    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 03:00:00',
   })
 # ---
 # name: test_calendar_events[time_tuple0-calendar.energy_site_sell_tariff][events]
   dict({
     'calendar.energy_site_sell_tariff': dict({
       'events': list([
-        dict({
-          'description': '''
-            Season: Summer
-            Period: On peak
-            Price: 0.16/kWh
-          ''',
-          'end': '2023-12-31T21:00:00-08:00',
-          'start': '2023-12-31T16:00:00-08:00',
-          'summary': 'On peak: 0.16/kWh',
-        }),
         dict({
           'description': '''
             Season: Summer
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-01T16:00:00-08:00',
-          'start': '2023-12-31T21:00:00-08:00',
+          'end': '2024-01-01T16:00:00+10:00',
+          'start': '2023-12-31T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -307,8 +307,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-01T21:00:00-08:00',
-          'start': '2024-01-01T16:00:00-08:00',
+          'end': '2024-01-01T21:00:00+10:00',
+          'start': '2024-01-01T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -317,8 +317,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-02T16:00:00-08:00',
-          'start': '2024-01-01T21:00:00-08:00',
+          'end': '2024-01-02T16:00:00+10:00',
+          'start': '2024-01-01T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -327,8 +327,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-02T21:00:00-08:00',
-          'start': '2024-01-02T16:00:00-08:00',
+          'end': '2024-01-02T21:00:00+10:00',
+          'start': '2024-01-02T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -337,8 +337,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-03T16:00:00-08:00',
-          'start': '2024-01-02T21:00:00-08:00',
+          'end': '2024-01-03T16:00:00+10:00',
+          'start': '2024-01-02T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -347,8 +347,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-03T21:00:00-08:00',
-          'start': '2024-01-03T16:00:00-08:00',
+          'end': '2024-01-03T21:00:00+10:00',
+          'start': '2024-01-03T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -357,8 +357,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-04T16:00:00-08:00',
-          'start': '2024-01-03T21:00:00-08:00',
+          'end': '2024-01-04T16:00:00+10:00',
+          'start': '2024-01-03T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -367,8 +367,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-04T21:00:00-08:00',
-          'start': '2024-01-04T16:00:00-08:00',
+          'end': '2024-01-04T21:00:00+10:00',
+          'start': '2024-01-04T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -377,8 +377,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-05T16:00:00-08:00',
-          'start': '2024-01-04T21:00:00-08:00',
+          'end': '2024-01-05T16:00:00+10:00',
+          'start': '2024-01-04T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -387,8 +387,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-05T21:00:00-08:00',
-          'start': '2024-01-05T16:00:00-08:00',
+          'end': '2024-01-05T21:00:00+10:00',
+          'start': '2024-01-05T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -397,8 +397,28 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-06T16:00:00-08:00',
-          'start': '2024-01-05T21:00:00-08:00',
+          'end': '2024-01-06T16:00:00+10:00',
+          'start': '2024-01-05T21:00:00+10:00',
+          'summary': 'Off peak: 0.08/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: On peak
+            Price: 0.16/kWh
+          ''',
+          'end': '2024-01-06T21:00:00+10:00',
+          'start': '2024-01-06T16:00:00+10:00',
+          'summary': 'On peak: 0.16/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: Off peak
+            Price: 0.08/kWh
+          ''',
+          'end': '2024-01-07T16:00:00+10:00',
+          'start': '2024-01-06T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
       ]),
@@ -413,35 +433,25 @@
       Period: On peak
       Price: 0.22/kWh
     ''',
-    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 21:00:00',
+    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 03:00:00',
     <EntityStateAttribute.FRIENDLY_NAME: 'friendly_name'>: 'Energy Site Buy tariff',
     <CalendarEntityStateAttribute.LOCATION: 'location'>: '',
     <CalendarEntityStateAttribute.MESSAGE: 'message'>: 'On peak: 0.22/kWh',
-    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2024-01-01 16:00:00',
+    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 22:00:00',
   })
 # ---
 # name: test_calendar_events[time_tuple1-calendar.energy_site_buy_tariff][events]
   dict({
     'calendar.energy_site_buy_tariff': dict({
       'events': list([
-        dict({
-          'description': '''
-            Season: Summer
-            Period: On peak
-            Price: 0.22/kWh
-          ''',
-          'end': '2023-12-31T21:00:00-08:00',
-          'start': '2023-12-31T16:00:00-08:00',
-          'summary': 'On peak: 0.22/kWh',
-        }),
         dict({
           'description': '''
             Season: Summer
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-01T16:00:00-08:00',
-          'start': '2023-12-31T21:00:00-08:00',
+          'end': '2024-01-01T16:00:00+10:00',
+          'start': '2023-12-31T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -450,8 +460,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-01T21:00:00-08:00',
-          'start': '2024-01-01T16:00:00-08:00',
+          'end': '2024-01-01T21:00:00+10:00',
+          'start': '2024-01-01T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -460,8 +470,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-02T16:00:00-08:00',
-          'start': '2024-01-01T21:00:00-08:00',
+          'end': '2024-01-02T16:00:00+10:00',
+          'start': '2024-01-01T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -470,8 +480,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-02T21:00:00-08:00',
-          'start': '2024-01-02T16:00:00-08:00',
+          'end': '2024-01-02T21:00:00+10:00',
+          'start': '2024-01-02T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -480,8 +490,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-03T16:00:00-08:00',
-          'start': '2024-01-02T21:00:00-08:00',
+          'end': '2024-01-03T16:00:00+10:00',
+          'start': '2024-01-02T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -490,8 +500,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-03T21:00:00-08:00',
-          'start': '2024-01-03T16:00:00-08:00',
+          'end': '2024-01-03T21:00:00+10:00',
+          'start': '2024-01-03T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -500,8 +510,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-04T16:00:00-08:00',
-          'start': '2024-01-03T21:00:00-08:00',
+          'end': '2024-01-04T16:00:00+10:00',
+          'start': '2024-01-03T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -510,8 +520,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-04T21:00:00-08:00',
-          'start': '2024-01-04T16:00:00-08:00',
+          'end': '2024-01-04T21:00:00+10:00',
+          'start': '2024-01-04T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -520,8 +530,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-05T16:00:00-08:00',
-          'start': '2024-01-04T21:00:00-08:00',
+          'end': '2024-01-05T16:00:00+10:00',
+          'start': '2024-01-04T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -530,8 +540,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-05T21:00:00-08:00',
-          'start': '2024-01-05T16:00:00-08:00',
+          'end': '2024-01-05T21:00:00+10:00',
+          'start': '2024-01-05T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -540,8 +550,28 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-06T16:00:00-08:00',
-          'start': '2024-01-05T21:00:00-08:00',
+          'end': '2024-01-06T16:00:00+10:00',
+          'start': '2024-01-05T21:00:00+10:00',
+          'summary': 'Off peak: 0.20/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: On peak
+            Price: 0.22/kWh
+          ''',
+          'end': '2024-01-06T21:00:00+10:00',
+          'start': '2024-01-06T16:00:00+10:00',
+          'summary': 'On peak: 0.22/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: Off peak
+            Price: 0.20/kWh
+          ''',
+          'end': '2024-01-07T16:00:00+10:00',
+          'start': '2024-01-06T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
       ]),
@@ -556,35 +586,25 @@
       Period: On peak
       Price: 0.16/kWh
     ''',
-    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 21:00:00',
+    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 03:00:00',
     <EntityStateAttribute.FRIENDLY_NAME: 'friendly_name'>: 'Energy Site Sell tariff',
     <CalendarEntityStateAttribute.LOCATION: 'location'>: '',
     <CalendarEntityStateAttribute.MESSAGE: 'message'>: 'On peak: 0.16/kWh',
-    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2024-01-01 16:00:00',
+    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2023-12-31 22:00:00',
   })
 # ---
 # name: test_calendar_events[time_tuple1-calendar.energy_site_sell_tariff][events]
   dict({
     'calendar.energy_site_sell_tariff': dict({
       'events': list([
-        dict({
-          'description': '''
-            Season: Summer
-            Period: On peak
-            Price: 0.16/kWh
-          ''',
-          'end': '2023-12-31T21:00:00-08:00',
-          'start': '2023-12-31T16:00:00-08:00',
-          'summary': 'On peak: 0.16/kWh',
-        }),
         dict({
           'description': '''
             Season: Summer
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-01T16:00:00-08:00',
-          'start': '2023-12-31T21:00:00-08:00',
+          'end': '2024-01-01T16:00:00+10:00',
+          'start': '2023-12-31T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -593,8 +613,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-01T21:00:00-08:00',
-          'start': '2024-01-01T16:00:00-08:00',
+          'end': '2024-01-01T21:00:00+10:00',
+          'start': '2024-01-01T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -603,8 +623,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-02T16:00:00-08:00',
-          'start': '2024-01-01T21:00:00-08:00',
+          'end': '2024-01-02T16:00:00+10:00',
+          'start': '2024-01-01T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -613,8 +633,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-02T21:00:00-08:00',
-          'start': '2024-01-02T16:00:00-08:00',
+          'end': '2024-01-02T21:00:00+10:00',
+          'start': '2024-01-02T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -623,8 +643,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-03T16:00:00-08:00',
-          'start': '2024-01-02T21:00:00-08:00',
+          'end': '2024-01-03T16:00:00+10:00',
+          'start': '2024-01-02T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -633,8 +653,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-03T21:00:00-08:00',
-          'start': '2024-01-03T16:00:00-08:00',
+          'end': '2024-01-03T21:00:00+10:00',
+          'start': '2024-01-03T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -643,8 +663,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-04T16:00:00-08:00',
-          'start': '2024-01-03T21:00:00-08:00',
+          'end': '2024-01-04T16:00:00+10:00',
+          'start': '2024-01-03T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -653,8 +673,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-04T21:00:00-08:00',
-          'start': '2024-01-04T16:00:00-08:00',
+          'end': '2024-01-04T21:00:00+10:00',
+          'start': '2024-01-04T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -663,8 +683,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-05T16:00:00-08:00',
-          'start': '2024-01-04T21:00:00-08:00',
+          'end': '2024-01-05T16:00:00+10:00',
+          'start': '2024-01-04T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -673,8 +693,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-05T21:00:00-08:00',
-          'start': '2024-01-05T16:00:00-08:00',
+          'end': '2024-01-05T21:00:00+10:00',
+          'start': '2024-01-05T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -683,8 +703,28 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-06T16:00:00-08:00',
-          'start': '2024-01-05T21:00:00-08:00',
+          'end': '2024-01-06T16:00:00+10:00',
+          'start': '2024-01-05T21:00:00+10:00',
+          'summary': 'Off peak: 0.08/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: On peak
+            Price: 0.16/kWh
+          ''',
+          'end': '2024-01-06T21:00:00+10:00',
+          'start': '2024-01-06T16:00:00+10:00',
+          'summary': 'On peak: 0.16/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: Off peak
+            Price: 0.08/kWh
+          ''',
+          'end': '2024-01-07T16:00:00+10:00',
+          'start': '2024-01-06T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
       ]),
@@ -699,35 +739,25 @@
       Period: Off peak
       Price: 0.20/kWh
     ''',
-    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-02 16:00:00',
+    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 22:00:00',
     <EntityStateAttribute.FRIENDLY_NAME: 'friendly_name'>: 'Energy Site Buy tariff',
     <CalendarEntityStateAttribute.LOCATION: 'location'>: '',
     <CalendarEntityStateAttribute.MESSAGE: 'message'>: 'Off peak: 0.20/kWh',
-    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2024-01-01 21:00:00',
+    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2024-01-01 03:00:00',
   })
 # ---
 # name: test_calendar_events[time_tuple2-calendar.energy_site_buy_tariff][events]
   dict({
     'calendar.energy_site_buy_tariff': dict({
       'events': list([
-        dict({
-          'description': '''
-            Season: Summer
-            Period: On peak
-            Price: 0.22/kWh
-          ''',
-          'end': '2023-12-31T21:00:00-08:00',
-          'start': '2023-12-31T16:00:00-08:00',
-          'summary': 'On peak: 0.22/kWh',
-        }),
         dict({
           'description': '''
             Season: Summer
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-01T16:00:00-08:00',
-          'start': '2023-12-31T21:00:00-08:00',
+          'end': '2024-01-01T16:00:00+10:00',
+          'start': '2023-12-31T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -736,8 +766,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-01T21:00:00-08:00',
-          'start': '2024-01-01T16:00:00-08:00',
+          'end': '2024-01-01T21:00:00+10:00',
+          'start': '2024-01-01T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -746,8 +776,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-02T16:00:00-08:00',
-          'start': '2024-01-01T21:00:00-08:00',
+          'end': '2024-01-02T16:00:00+10:00',
+          'start': '2024-01-01T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -756,8 +786,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-02T21:00:00-08:00',
-          'start': '2024-01-02T16:00:00-08:00',
+          'end': '2024-01-02T21:00:00+10:00',
+          'start': '2024-01-02T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -766,8 +796,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-03T16:00:00-08:00',
-          'start': '2024-01-02T21:00:00-08:00',
+          'end': '2024-01-03T16:00:00+10:00',
+          'start': '2024-01-02T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -776,8 +806,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-03T21:00:00-08:00',
-          'start': '2024-01-03T16:00:00-08:00',
+          'end': '2024-01-03T21:00:00+10:00',
+          'start': '2024-01-03T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -786,8 +816,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-04T16:00:00-08:00',
-          'start': '2024-01-03T21:00:00-08:00',
+          'end': '2024-01-04T16:00:00+10:00',
+          'start': '2024-01-03T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -796,8 +826,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-04T21:00:00-08:00',
-          'start': '2024-01-04T16:00:00-08:00',
+          'end': '2024-01-04T21:00:00+10:00',
+          'start': '2024-01-04T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -806,8 +836,8 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-05T16:00:00-08:00',
-          'start': '2024-01-04T21:00:00-08:00',
+          'end': '2024-01-05T16:00:00+10:00',
+          'start': '2024-01-04T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
         dict({
@@ -816,8 +846,8 @@
             Period: On peak
             Price: 0.22/kWh
           ''',
-          'end': '2024-01-05T21:00:00-08:00',
-          'start': '2024-01-05T16:00:00-08:00',
+          'end': '2024-01-05T21:00:00+10:00',
+          'start': '2024-01-05T16:00:00+10:00',
           'summary': 'On peak: 0.22/kWh',
         }),
         dict({
@@ -826,8 +856,28 @@
             Period: Off peak
             Price: 0.20/kWh
           ''',
-          'end': '2024-01-06T16:00:00-08:00',
-          'start': '2024-01-05T21:00:00-08:00',
+          'end': '2024-01-06T16:00:00+10:00',
+          'start': '2024-01-05T21:00:00+10:00',
+          'summary': 'Off peak: 0.20/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: On peak
+            Price: 0.22/kWh
+          ''',
+          'end': '2024-01-06T21:00:00+10:00',
+          'start': '2024-01-06T16:00:00+10:00',
+          'summary': 'On peak: 0.22/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: Off peak
+            Price: 0.20/kWh
+          ''',
+          'end': '2024-01-07T16:00:00+10:00',
+          'start': '2024-01-06T21:00:00+10:00',
           'summary': 'Off peak: 0.20/kWh',
         }),
       ]),
@@ -842,35 +892,25 @@
       Period: Off peak
       Price: 0.08/kWh
     ''',
-    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-02 16:00:00',
+    <CalendarEntityStateAttribute.END_TIME: 'end_time'>: '2024-01-01 22:00:00',
     <EntityStateAttribute.FRIENDLY_NAME: 'friendly_name'>: 'Energy Site Sell tariff',
     <CalendarEntityStateAttribute.LOCATION: 'location'>: '',
     <CalendarEntityStateAttribute.MESSAGE: 'message'>: 'Off peak: 0.08/kWh',
-    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2024-01-01 21:00:00',
+    <CalendarEntityStateAttribute.START_TIME: 'start_time'>: '2024-01-01 03:00:00',
   })
 # ---
 # name: test_calendar_events[time_tuple2-calendar.energy_site_sell_tariff][events]
   dict({
     'calendar.energy_site_sell_tariff': dict({
       'events': list([
-        dict({
-          'description': '''
-            Season: Summer
-            Period: On peak
-            Price: 0.16/kWh
-          ''',
-          'end': '2023-12-31T21:00:00-08:00',
-          'start': '2023-12-31T16:00:00-08:00',
-          'summary': 'On peak: 0.16/kWh',
-        }),
         dict({
           'description': '''
             Season: Summer
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-01T16:00:00-08:00',
-          'start': '2023-12-31T21:00:00-08:00',
+          'end': '2024-01-01T16:00:00+10:00',
+          'start': '2023-12-31T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -879,8 +919,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-01T21:00:00-08:00',
-          'start': '2024-01-01T16:00:00-08:00',
+          'end': '2024-01-01T21:00:00+10:00',
+          'start': '2024-01-01T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -889,8 +929,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-02T16:00:00-08:00',
-          'start': '2024-01-01T21:00:00-08:00',
+          'end': '2024-01-02T16:00:00+10:00',
+          'start': '2024-01-01T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -899,8 +939,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-02T21:00:00-08:00',
-          'start': '2024-01-02T16:00:00-08:00',
+          'end': '2024-01-02T21:00:00+10:00',
+          'start': '2024-01-02T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -909,8 +949,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-03T16:00:00-08:00',
-          'start': '2024-01-02T21:00:00-08:00',
+          'end': '2024-01-03T16:00:00+10:00',
+          'start': '2024-01-02T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -919,8 +959,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-03T21:00:00-08:00',
-          'start': '2024-01-03T16:00:00-08:00',
+          'end': '2024-01-03T21:00:00+10:00',
+          'start': '2024-01-03T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -929,8 +969,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-04T16:00:00-08:00',
-          'start': '2024-01-03T21:00:00-08:00',
+          'end': '2024-01-04T16:00:00+10:00',
+          'start': '2024-01-03T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -939,8 +979,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-04T21:00:00-08:00',
-          'start': '2024-01-04T16:00:00-08:00',
+          'end': '2024-01-04T21:00:00+10:00',
+          'start': '2024-01-04T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -949,8 +989,8 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-05T16:00:00-08:00',
-          'start': '2024-01-04T21:00:00-08:00',
+          'end': '2024-01-05T16:00:00+10:00',
+          'start': '2024-01-04T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
         dict({
@@ -959,8 +999,8 @@
             Period: On peak
             Price: 0.16/kWh
           ''',
-          'end': '2024-01-05T21:00:00-08:00',
-          'start': '2024-01-05T16:00:00-08:00',
+          'end': '2024-01-05T21:00:00+10:00',
+          'start': '2024-01-05T16:00:00+10:00',
           'summary': 'On peak: 0.16/kWh',
         }),
         dict({
@@ -969,8 +1009,28 @@
             Period: Off peak
             Price: 0.08/kWh
           ''',
-          'end': '2024-01-06T16:00:00-08:00',
-          'start': '2024-01-05T21:00:00-08:00',
+          'end': '2024-01-06T16:00:00+10:00',
+          'start': '2024-01-05T21:00:00+10:00',
+          'summary': 'Off peak: 0.08/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: On peak
+            Price: 0.16/kWh
+          ''',
+          'end': '2024-01-06T21:00:00+10:00',
+          'start': '2024-01-06T16:00:00+10:00',
+          'summary': 'On peak: 0.16/kWh',
+        }),
+        dict({
+          'description': '''
+            Season: Summer
+            Period: Off peak
+            Price: 0.08/kWh
+          ''',
+          'end': '2024-01-07T16:00:00+10:00',
+          'start': '2024-01-06T21:00:00+10:00',
           'summary': 'Off peak: 0.08/kWh',
         }),
       ]),
diff --git a/tests/components/teslemetry/test_calendar.py b/tests/components/teslemetry/test_calendar.py
index ca5a2ed29722..ea3556ba63ab 100644
--- a/tests/components/teslemetry/test_calendar.py
+++ b/tests/components/teslemetry/test_calendar.py
@@ -31,6 +31,7 @@ from .const import SITE_INFO, SITE_INFO_MULTI_SEASON, SITE_INFO_WEEK_CROSSING
 ENTITY_BUY = "calendar.energy_site_buy_tariff"
 ENTITY_SELL = "calendar.energy_site_sell_tariff"
 ENTITY_OPERATION_MODE = "select.energy_site_operation_mode"
+SITE_TIME_ZONE = dt_util.get_time_zone("Australia/Brisbane")
 
 TARIFF_V2 = SITE_INFO["response"]["tariff_content_v2"]
 SLIM_SITE_INFO = {
@@ -141,7 +142,7 @@ async def test_calendar(
     mock_legacy: AsyncMock,
 ) -> None:
     """Tests that the calendar entity is correct."""
-    tz = dt_util.get_default_time_zone()
+    tz = SITE_TIME_ZONE
     freezer.move_to(datetime(2024, 1, 1, 10, 0, 0, tzinfo=tz))
 
     entry = await setup_platform(hass, [Platform.CALENDAR])
@@ -149,6 +150,27 @@ async def test_calendar(
     assert_entities(hass, entry.entry_id, entity_registry, snapshot)
 
 
+@pytest.mark.usefixtures("entity_registry_enabled_by_default")
+async def test_calendar_site_time_zone(
+    hass: HomeAssistant,
+    freezer: FrozenDateTimeFactory,
+    mock_legacy: AsyncMock,
+) -> None:
+    """Test the tariff is evaluated in the site timezone, not the Home Assistant one."""
+    await hass.config.async_set_time_zone("US/Pacific")
+    # 17:00 at the Australia/Brisbane site, inside ON_PEAK 16-21
+    freezer.move_to("2024-01-01T07:00:00Z")
+
+    await setup_platform(hass, [Platform.CALENDAR])
+
+    state = hass.states.get(ENTITY_BUY)
+    assert state
+    assert state.state == "on"
+    assert state.attributes["message"] == "On peak: 0.22/kWh"
+    assert state.attributes["start_time"] == "2023-12-31 22:00:00"
+    assert state.attributes["end_time"] == "2024-01-01 03:00:00"
+
+
 @pytest.mark.parametrize(
     "entity_id",
     [ENTITY_BUY, ENTITY_SELL],
@@ -172,7 +194,7 @@ async def test_calendar_events(
     time_tuple: tuple,
 ) -> None:
     """Tests that the energy tariff calendar entity events are correct."""
-    tz = dt_util.get_default_time_zone()
+    tz = SITE_TIME_ZONE
     freezer.move_to(datetime(*time_tuple, tzinfo=tz))
 
     await setup_platform(hass, [Platform.CALENDAR])
@@ -383,7 +405,7 @@ async def test_calendar_midnight_crossing_local_start(
     mock_legacy: AsyncMock,
 ) -> None:
     """Test async_get_events includes overnight period at local midnight."""
-    tz = dt_util.get_default_time_zone()
+    tz = SITE_TIME_ZONE
     freezer.move_to(datetime(2024, 1, 1, 10, 0, 0, tzinfo=tz))
 
     await setup_platform(hass, [Platform.CALENDAR])
@@ -435,7 +457,7 @@ async def test_calendar_end_of_day_period(
     mock_site_info_end_of_day: AsyncMock,
 ) -> None:
     """Test a tariff period ending at the day boundary parses instead of crashing."""
-    tz = dt_util.get_default_time_zone()
+    tz = SITE_TIME_ZONE
     # Sunday 23:45, inside the 23:30->24:00 end-of-day period
     freezer.move_to(datetime(2024, 1, 7, 23, 45, 0, tzinfo=tz))