Simplify timezone handling

astimezone() assumes the system local timezone if called without
arguments .

https://docs.python.org/3.10/library/datetime.html#datetime.datetime.astimezone

This is a API break as it removes the local_zone symbol.

Author: jspricke

docs/index.rst

@@ -359,8 +359,7 @@ If you want to compare datetime aware value with datetime naive value, you need
 to localize the naive value first:
 
     >>> from datetime import datetime
-    >>> from tasklib.task import local_zone
-    >>> now = datetime.now().replace(tzinfo=local_zone)
+    >>> now = datetime.now().astimezone()
     >>> t['due'] = now
     >>> now
     datetime.datetime(2015, 2, 1, 19, 44, 4, 770001, tzinfo=<DstTzInfo 'Europe/Berlin' CET+1:00:00 STD>)

tasklib/__init__.py

@@ -1,5 +1,4 @@
 from .backends import TaskWarrior
 from .task import Task
-from .serializing import local_zone
 
 __version__ = '2.5.0'

tasklib/backends.py

@@ -10,7 +10,6 @@
 
 from .task import Task, TaskQuerySet, ReadOnlyDictView
 from .filters import TaskWarriorFilter
-from .serializing import local_zone
 
 DATE_FORMAT_CALC = '%Y-%m-%dT%H:%M:%S'
 
@@ -225,7 +224,7 @@ def convert_datetime_string(self, value):
         args = value.split()
         result = self.execute_command(['calc'] + args)
         naive = datetime.datetime.strptime(result[0], DATE_FORMAT_CALC)
-        localized = naive.replace(tzinfo=local_zone)
+        localized = naive.astimezone()
         return localized
 
     @property

tasklib/serializing.py

@@ -10,7 +10,6 @@
 from .lazy import LazyUUIDTaskSet, LazyUUIDTask
 
 DATE_FORMAT = '%Y%m%dT%H%M%SZ'
-local_zone = ZoneInfo('localtime')
 
 
 class SerializingObject(object):
@@ -86,7 +85,7 @@ def timestamp_deserializer(self, date_str):
         # Return timestamp localized in the local zone
         naive_timestamp = datetime.datetime.strptime(date_str, DATE_FORMAT)
         localized_timestamp = naive_timestamp.replace(tzinfo=ZoneInfo('UTC'))
-        return localized_timestamp.astimezone(local_zone)
+        return localized_timestamp.astimezone()
 
     def serialize_entry(self, value):
         return self.timestamp_serializer(value)
@@ -228,11 +227,11 @@ def datetime_normalizer(self, value):
         ):
             # Convert to local midnight
             value_full = datetime.datetime.combine(value, datetime.time.min)
-            localized = value_full.replace(tzinfo=local_zone)
+            localized = value_full.astimezone()
         elif isinstance(value, datetime.datetime):
             if value.tzinfo is None:
                 # Convert to localized datetime object
-                localized = value.replace(tzinfo=local_zone)
+                localized = value.astimezone()
             else:
                 # If the value is already localized, there is no need to change
                 # time zone at this point. Also None is a valid value too.

tasklib/task.py

@@ -7,7 +7,7 @@
 import os
 import sys
 
-from .serializing import SerializingObject, local_zone
+from .serializing import SerializingObject
 
 DATE_FORMAT = '%Y%m%dT%H%M%SZ'
 REPR_OUTPUT_SIZE = 10
@@ -299,7 +299,7 @@ def waiting(self):
         if not self['wait']:
             return False
 
-        return self['wait'] > datetime.datetime.now().replace(tzinfo=local_zone)
+        return self['wait'] > datetime.datetime.now().astimezone()
 
     @property
     def pending(self):

tasklib/tests.py

@@ -18,7 +18,7 @@
 from .backends import TaskWarrior
 from .task import Task, ReadOnlyDictView
 from .lazy import LazyUUIDTask, LazyUUIDTaskSet
-from .serializing import DATE_FORMAT, local_zone
+from .serializing import DATE_FORMAT
 
 # http://taskwarrior.org/docs/design/task.html , Section: The Attributes
 TASK_STANDARD_ATTRS = (
@@ -1134,10 +1134,9 @@ class TimezoneAwareDatetimeTest(TasklibTest):
 
     def setUp(self):
         super(TimezoneAwareDatetimeTest, self).setUp()
-        self.zone = local_zone
         self.localdate_naive = datetime.datetime(2015, 2, 2)
         self.localtime_naive = datetime.datetime(2015, 2, 2, 0, 0, 0)
-        self.localtime_aware = self.localtime_naive.replace(tzinfo=self.zone)
+        self.localtime_aware = self.localtime_naive.astimezone()
         self.utctime_aware = self.localtime_aware.astimezone(ZoneInfo('UTC'))
 
     def test_timezone_naive_datetime_setitem(self):
@@ -1219,7 +1218,7 @@ def test_simple_now_conversion(self):
                 return
 
         t = Task(self.tw, description='test task', due='now')
-        now = datetime.datetime.now().replace(tzinfo=local_zone)
+        now = datetime.datetime.now().astimezone()
 
         # Assert that both times are not more than 5 seconds apart
         if sys.version_info < (2, 7):
@@ -1239,16 +1238,15 @@ def test_simple_eoy_conversion(self):
                 return
 
         t = Task(self.tw, description='test task', due='eoy')
-        now = datetime.datetime.now().replace(tzinfo=local_zone)
+        now = datetime.datetime.now().astimezone()
         eoy = datetime.datetime(
             year=now.year,
             month=12,
             day=31,
             hour=23,
             minute=59,
             second=59,
-            tzinfo=local_zone
-        )
+        ).astimezone()
         if self.tw.version >= '2.5.2' and self.tw.version < '2.6.0':
             eoy = datetime.datetime(
                 year=now.year+1,
@@ -1257,8 +1255,7 @@ def test_simple_eoy_conversion(self):
                 hour=0,
                 minute=0,
                 second=0,
-                tzinfo=local_zone
-            )
+            ).astimezone()
         self.assertEqual(eoy, t['due'])
 
     def test_complex_eoy_conversion(self):
@@ -1271,16 +1268,15 @@ def test_complex_eoy_conversion(self):
                 return
 
         t = Task(self.tw, description='test task', due='eoy - 2 months')
-        now = datetime.datetime.now().replace(tzinfo=local_zone)
+        now = datetime.datetime.now().astimezone()
         due_date = datetime.datetime(
             year=now.year,
             month=12,
             day=31,
             hour=23,
             minute=59,
             second=59,
-            tzinfo=local_zone
-        ) - datetime.timedelta(0, 2 * 30 * 86400)
+        ).astimezone() - datetime.timedelta(0, 2 * 30 * 86400)
         if self.tw.version >= '2.5.2' and self.tw.version < '2.6.0':
             due_date = datetime.datetime(
                 year=now.year+1,
@@ -1289,8 +1285,7 @@ def test_complex_eoy_conversion(self):
                 hour=0,
                 minute=0,
                 second=0,
-                tzinfo=local_zone
-            ) - datetime.timedelta(0, 2 * 30 * 86400)
+            ).astimezone() - datetime.timedelta(0, 2 * 30 * 86400)
         self.assertEqual(due_date, t['due'])
 
     def test_filtering_with_string_datetime(self):