DateUtils (addToDate): compute day offset in local time manner.

if timezone is Europe/Paris, we expect :

'2021/03/28' + 1 day => '2021/03/29 GMT+1', NOT '2021/03/29 GMT+2.

i.e. 'same time' in the next day.

'2021/03/28' + 3 hours => '2021/03/28 04:00 GMT+2', NOT '2021/03/28 03:00 GMT+1'.

i.e. valid timezone offset at the result time.

bt5/erp5_core_test/TestTemplateItem/portal_components/test.erp5.testDateUtils.py

@@ -27,12 +27,20 @@
 #
 ##############################################################################
 
+import os
+import time
 import unittest
 
 from DateTime import DateTime
 from erp5.component.module.DateUtils import addToDate, getIntervalListBetweenDates, \
     atTheEndOfPeriod, getClosestDate
 
+os.environ['TZ']='Europe/Paris'
+time.tzset()
+DateTime._localzone0 = 'GMT+1'
+DateTime._localzone1 = 'GMT+2'
+DateTime._multipleZones = True
+
 class TestDateUtils(unittest.TestCase):
   """
   Tests DateUtils
@@ -175,6 +183,32 @@ class TestDateUtils(unittest.TestCase):
     self.assertEqual('Sep. 10, 2008 12:00 am GMT-2',
       getClosestDate(date=date, target_date=target_date, precision='month', before=False).pCommonZ())
 
+  def test_implicit_local_time(self):
+    self.assertEqual(
+      str(addToDate(DateTime('2020/03/10'), month=1)),
+      '2020/04/10 00:00:00 GMT+2',
+    )
+    self.assertEqual(
+      str(addToDate(DateTime('2020/10/20'), month=1)),
+      '2020/11/20 00:00:00 GMT+1',
+    )
+    self.assertEqual(
+      str(addToDate(DateTime('2020/03/29'), day=1)),
+      '2020/03/30 00:00:00 GMT+2',
+    )
+    self.assertEqual(
+      str(addToDate(DateTime('2020/10/25'), day=1)),
+      '2020/10/26 00:00:00 GMT+1',
+    )
+    self.assertEqual(
+      str(addToDate(DateTime('2020/03/29 00:30:00.123456'), hour=3)),
+      '2020/03/29 04:30:0.123456 GMT+2',
+    )
+    self.assertEqual(
+      str(addToDate(DateTime('2020/10/25 00:30:00.123456'), hour=3)),
+      '2020/10/25 02:30:0.123456 GMT+1',
+    )
+
 def test_suite():
   suite = unittest.TestSuite()
   suite.addTest(unittest.makeSuite(TestDateUtils))

product/ERP5/bootstrap/erp5_core/ModuleComponentTemplateItem/portal_components/module.erp5.DateUtils.py

@@ -129,15 +129,23 @@ def addToDate(date, to_add=None, **kw):
   if to_add.get('day', None) is not None:
     day_to_add += to_add['day']
   return_value['day'] = 1
-  return_date = DateTime('%i/%i/%i %i:%i:%d %s' % (return_value['year'],
+  # compute year/month/date with UTC to ignore possible offset change.
+  return_date = DateTime('%i/%i/%i UTC' % (return_value['year'],
                                            return_value['month'],
-                                                return_value['day'],
-                                                return_value['hour'],
-                                                return_value['minute'],
-                                                return_value['second'],
-                                                date.timezone()))
+                                           return_value['day'],))
 
   return_date += day_to_add
+  timezone = date.timezone()
+  if DateTime(date.strftime('%Y/%m/%d %H:%M:%S.%f')).timezone() == timezone:
+    # assume date has local timezone.
+    timezone = ''
+  return_date = DateTime(return_date.strftime('%Y/%m/%d ' + timezone)) + \
+    return_value['hour'] / 24. + \
+    return_value['minute'] / 1440. + \
+    return_value['second'] / 86400.
+  if not timezone:
+    # convert to valid local time at return_date timing.
+    return_date = DateTime(float(return_date))
   return return_date
 
 def getClosestDate(date=None, target_date=None,