[Dayone] don't break if the system timezone is UTC

jrnl/DayOneJournal.py

@@ -52,7 +52,16 @@ class DayOne(Journal.Journal):
                     except (KeyError, pytz.exceptions.UnknownTimeZoneError):
                         timezone = tzlocal.get_localzone()
                     date = dict_entry["Creation Date"]
-                    date = date + timezone.utcoffset(date, is_dst=False)
+                    try:
+                        date = date + timezone.utcoffset(date, is_dst=False)
+                    except TypeError:
+                        # The above converts the date to UTC. However, if the
+                        # timezone is already in UTC, you can't call
+                        # timezone.utcoffset() with the is_dst parameter
+                        # ("utcoffset() got an unexpected keyword argument
+                        # 'is_dst'"), but we already have our date in UTC, so
+                        # nothing more needs to be done.
+                        pass
                     entry = Entry.Entry(
                         self,
                         date,