diff --git a/addons/calendar/models/calendar.py b/addons/calendar/models/calendar.py
index 25377659563..8ec5dcb195c 100644
--- a/addons/calendar/models/calendar.py
+++ b/addons/calendar/models/calendar.py
@@ -890,18 +890,18 @@ class Meeting(models.Model):
     def _inverse_dates(self):
         for meeting in self:
             if meeting.allday:
-                tz = pytz.timezone(self.env.user.tz) if self.env.user.tz else pytz.utc
 
+                # Convention break:
+                # stop and start are NOT in UTC in allday event
+                # in this case, they actually represent a date
+                # i.e. Christmas is on 25/12 for everyone
+                # even if people don't celebrate it simultaneously
                 enddate = fields.Datetime.from_string(meeting.stop_date)
-                enddate = tz.localize(enddate)
                 enddate = enddate.replace(hour=18)
-                enddate = enddate.astimezone(pytz.utc)
                 meeting.stop = fields.Datetime.to_string(enddate)
 
                 startdate = fields.Datetime.from_string(meeting.start_date)
-                startdate = tz.localize(startdate)  # Add "+hh:mm" timezone
-                startdate = startdate.replace(hour=8)  # Set 8 AM in localtime
-                startdate = startdate.astimezone(pytz.utc)  # Convert to UTC
+                startdate = startdate.replace(hour=8)  # Set 8 AM
                 meeting.start = fields.Datetime.to_string(startdate)
             else:
                 meeting.write({'start': meeting.start_datetime,
diff --git a/addons/calendar/tests/test_calendar.py b/addons/calendar/tests/test_calendar.py
index 12547c8f695..e04866f1f68 100644
--- a/addons/calendar/tests/test_calendar.py
+++ b/addons/calendar/tests/test_calendar.py
@@ -275,3 +275,20 @@ class TestCalendar(TransactionCase):
         self.assertEqual(test_event.res_model, test_record._name)
         self.assertEqual(test_event.res_id, test_record.id)
         self.assertEqual(len(test_record.activity_ids), 1)
+
+    def test_event_allday(self):
+        self.env.user.tz = 'Pacific/Honolulu'
+
+        event = self.CalendarEvent.create({
+            'name': 'All Day',
+            'start': "2018-10-16 00:00:00",
+            'start_date': "2018-10-16",
+            'start_datetime': False,
+            'stop': "2018-10-18 00:00:00",
+            'stop_date': "2018-10-18",
+            'stop_datetime': False,
+            'allday': True,
+        })
+
+        self.assertEqual(event.start, '2018-10-16 08:00:00')
+        self.assertEqual(event.stop, '2018-10-18 18:00:00')