diff --git a/addons/base_import/models/base_import.py b/addons/base_import/models/base_import.py
index 7201b194193..09d2dcb2852 100644
--- a/addons/base_import/models/base_import.py
+++ b/addons/base_import/models/base_import.py
@@ -603,11 +603,13 @@ class Import(models.TransientModel):
                 server_format = DEFAULT_SERVER_DATE_FORMAT if field['type'] == 'date' else DEFAULT_SERVER_DATETIME_FORMAT
 
                 if options.get('%s_format' % field['type'], server_format) != server_format:
-                    user_format = ustr(options.get('%s_format' % field['type'])).encode('utf-8')
+                    # datetime.str[fp]time takes *native strings* in both
+                    # versions, for both data and pattern
+                    user_format = pycompat.to_native(options.get('%s_format' % field['type']))
                     for num, line in enumerate(data):
                         if line[index]:
                             try:
-                                line[index] = dt.strftime(dt.strptime(ustr(line[index].strip()).encode('utf-8'), user_format), server_format)
+                                line[index] = dt.strftime(dt.strptime(pycompat.to_native(line[index].strip()), user_format), server_format)
                             except ValueError as e:
                                 raise ValueError(_("Column %s contains incorrect values. Error in line %d: %s") % (name, num + 1, e))
                             except Exception as e:
diff --git a/addons/calendar/models/calendar.py b/addons/calendar/models/calendar.py
index a6656af1a5b..49c87a8e9b9 100644
--- a/addons/calendar/models/calendar.py
+++ b/addons/calendar/models/calendar.py
@@ -632,8 +632,8 @@ class Meeting(models.Model):
             }
 
         # formats will be used for str{f,p}time() which do not support unicode in Python 2, coerce to str
-        format_date = lang_params.get("date_format", '%B-%d-%Y').encode('utf-8')
-        format_time = lang_params.get("time_format", '%I-%M %p').encode('utf-8')
+        format_date = pycompat.to_native(lang_params.get("date_format", '%B-%d-%Y'))
+        format_time = pycompat.to_native(lang_params.get("time_format", '%I-%M %p'))
         return (format_date, format_time)
 
     @api.model
@@ -919,11 +919,11 @@ class Meeting(models.Model):
                     elif interval == 'minutes':
                         delta = timedelta(minutes=duration)
                     trigger.value = delta
-                    valarm.add('DESCRIPTION').value = alarm.name or 'Odoo'
+                    valarm.add('DESCRIPTION').value = alarm.name or u'Odoo'
             for attendee in meeting.attendee_ids:
                 attendee_add = event.add('attendee')
-                attendee_add.value = 'MAILTO:' + (attendee.email or '')
-            result[meeting.id] = cal.serialize()
+                attendee_add.value = u'MAILTO:' + (attendee.email or u'')
+            result[meeting.id] = cal.serialize().encode('utf-8')
 
         return result
 
diff --git a/addons/mail/models/mail_template.py b/addons/mail/models/mail_template.py
index f44ee7be09a..f3a7acb253b 100644
--- a/addons/mail/models/mail_template.py
+++ b/addons/mail/models/mail_template.py
@@ -45,7 +45,7 @@ def format_tz(env, dt, tz=False, format=False):
         return format_datetime(ts, format or 'medium', locale=env.context.get("lang") or 'en_US')
 
     if format:
-        return ts.strftime(format)
+        return pycompat.text_type(ts.strftime(format))
     else:
         lang = env.context.get("lang")
         langs = env['res.lang']
@@ -54,9 +54,9 @@ def format_tz(env, dt, tz=False, format=False):
         format_date = langs.date_format or '%B-%d-%Y'
         format_time = langs.time_format or '%I-%M %p'
 
-        fdate = ts.strftime(format_date).decode('utf-8')
-        ftime = ts.strftime(format_time).decode('utf-8')
-        return "%s %s%s" % (fdate, ftime, (' (%s)' % tz) if tz else '')
+        fdate = pycompat.text_type(ts.strftime(format_date))
+        ftime = pycompat.text_type(ts.strftime(format_time))
+        return u"%s %s%s" % (fdate, ftime, (u' (%s)' % tz) if tz else u'')
 
 def format_amount(env, amount, currency):
     fmt = "%.{0}f".format(currency.decimal_places)