TimeVariable: handle different timezones

Orange/data/variable.py

@@ -934,8 +934,9 @@ def __init__(self, date_string):
     # UTC offset and associated timezone. If parsed datetime values provide an
     # offset, it is used for display. If not all values have the same offset,
     # +0000 (=UTC) timezone is used and utc_offset is set to False.
-    _utc_offset = None
-    timezone = timezone.utc
+    _utc_offset = None  # deprecated
+    _different_timezones = False
+    _timezone = None
 
     def __init__(self, *args, have_date=0, have_time=0, **kwargs):
         super().__init__(*args, **kwargs)
@@ -958,6 +959,18 @@ def utc_offset(self, val):
         )
         self._utc_offset = val
 
+    @property
+    def timezone(self):
+        return self._timezone if self._timezone is not None else timezone.utc
+
+    @timezone.setter
+    def timezone(self, val):
+        if self._timezone is None and not self._different_timezones:
+            self._timezone = val
+        elif val != self.timezone:
+            self._timezone = None
+            self._different_timezones = True
+
     def copy(self, compute_value=Variable._CopyComputeValue, *, name=None, **_):
         return super().copy(compute_value=compute_value, name=name,
                             have_date=self.have_date, have_time=self.have_time)
@@ -1045,14 +1058,16 @@ def parse(self, datestr):
 
         # Remember UTC offset. If not all parsed values share the same offset,
         # remember none of it.
+        # when utc_offset is removed also this complete logic can be removed
+        # timezone setter will handle different timezones
         offset = dt.utcoffset()
         if self._utc_offset is not False:
             if offset and self._utc_offset is None:
                 self._utc_offset = offset
                 self.timezone = timezone(offset)
             elif self._utc_offset != offset:
                 self._utc_offset = False
-                self.timezone = timezone.utc
+                self.timezone = None
 
         # Convert time to UTC timezone. In dates without timezone,
         # localtime is assumed. See also: