diff --git a/addons/calendar/models/calendar.py b/addons/calendar/models/calendar.py
index 3fae81f860f..3c7e24c9187 100644
--- a/addons/calendar/models/calendar.py
+++ b/addons/calendar/models/calendar.py
@@ -670,27 +670,27 @@ class Meeting(models.Model):
                 1) if user add duration for 2 hours, return : August-23-2013 at (04-30 To 06-30) (Europe/Brussels)
                 2) if event all day ,return : AllDay, July-31-2013
         """
-        timezone = self._context.get('tz')
-        if not timezone:
-            timezone = self.env.user.partner_id.tz or 'UTC'
-        timezone = tools.ustr(timezone).encode('utf-8')  # make safe for str{p,f}time()
+        timezone = self._context.get('tz') or self.env.user.partner_id.tz or 'UTC'
+        timezone = pycompat.to_native(timezone)  # make safe for str{p,f}time()
 
         # get date/time format according to context
-        format_date, format_time = self.with_context(tz=timezone)._get_date_formats()
+        format_date, format_time = self._get_date_formats()
 
         # convert date and time into user timezone
-        date = fields.Datetime.context_timestamp(self.with_context(tz=timezone), fields.Datetime.from_string(start))
-        date_deadline = fields.Datetime.context_timestamp(self.with_context(tz=timezone), fields.Datetime.from_string(stop))
+        self_tz = self.with_context(tz=timezone)
+        date = fields.Datetime.context_timestamp(self_tz, fields.Datetime.from_string(start))
+        date_deadline = fields.Datetime.context_timestamp(self_tz, fields.Datetime.from_string(stop))
 
         # convert into string the date and time, using user formats
-        date_str = date.strftime(format_date).decode('utf-8')
-        time_str = date.strftime(format_time).decode('utf-8')
+        to_text = pycompat.to_text
+        date_str = to_text(date.strftime(format_date))
+        time_str = to_text(date.strftime(format_time))
 
         if zallday:
             display_time = _("AllDay , %s") % (date_str)
         elif zduration < 24:
             duration = date + timedelta(hours=zduration)
-            duration_time = duration.strftime(format_time).decode('utf-8')
+            duration_time = to_text(duration.strftime(format_time))
             display_time = _(u"%s at (%s To %s) (%s)") % (
                 date_str,
                 time_str,
@@ -698,8 +698,8 @@ class Meeting(models.Model):
                 timezone,
             )
         else:
-            dd_date = date_deadline.strftime(format_date).decode('utf-8')
-            dd_time = date_deadline.strftime(format_time).decode('utf-8')
+            dd_date = to_text(date_deadline.strftime(format_date))
+            dd_time = to_text(date_deadline.strftime(format_time))
             display_time = _(u"%s at %s To\n %s at %s (%s)") % (
                 date_str,
                 time_str,