calendar: use addToDate function to manipulate DateTime.

It allows to create new DateTime with the same timezone.

bt5/erp5_hr_calendar/WorkflowTemplateItem/portal_workflow/hr_calendar_interaction_workflow/scripts/TimeTableLine_afterEdit.xml

@@ -55,6 +55,7 @@
 # automatically set a good start and stop date to make generic code working\n
 \n
 from DateTime import DateTime\n
+from Products.ERP5Type.DateUtils import addToDate\n
 time_table_line = state_change["object"]\n
 \n
 day_of_week = time_table_line.getDayOfWeek()\n
@@ -63,9 +64,9 @@ if not(None in (day_of_week, quantity)):\n
   time_table_line.setPeriodicityWeekDayList([day_of_week])\n
   start_date = DateTime("2014/04/01")\n
   while start_date.Day() != day_of_week:\n
-    start_date = start_date + 1\n
+    start_date = addToDate(start_date, day=1)\n
   time_table_line.setStartDate(start_date)\n
-  stop_date = start_date + 1.0/24*quantity\n
+  stop_date = addToDate(start_date, hour=quantity)\n
   time_table_line.setStopDate(stop_date)\n
 # after change, make sure to update group calendars through the usual alarm\n
 context.getPortalObject().portal_alarms.update_time_table_end_periodicity.activate(\n

product/ERP5/Document/PresencePeriod.py

@@ -152,7 +152,7 @@ class PresencePeriod(Movement, PeriodicityMixin):
       second_duration = int(stop_date) - int(start_date)
       if second_duration > 0:
         # First date has to respect the periodicity config
-        next_start_date = self.getNextPeriodicalDate(start_date-1)
+        next_start_date = self.getNextPeriodicalDate(addToDate(start_date, day=-1))
         while (next_start_date is not None) and \
           (next_start_date <= periodicity_stop_date):