diff --git a/SoObjects/Appointments/SOGoAppointmentObject.m b/SoObjects/Appointments/SOGoAppointmentObject.m
index 1f7dc9132..6528e0a6b 100644
--- a/SoObjects/Appointments/SOGoAppointmentObject.m
+++ b/SoObjects/Appointments/SOGoAppointmentObject.m
@@ -639,12 +639,17 @@
   NSEnumerator *enumerator;
   NSString *currentUID;
   SOGoUser *user, *currentUser;
+  unsigned long long eventStartPeriod, eventEndPeriod;
 
   _resourceHasAutoAccepted = NO;
 
   // Build a list of the attendees uids
   attendees = [NSMutableArray arrayWithCapacity: [theAttendees count]];
   enumerator = [theAttendees objectEnumerator];
+
+  eventStartPeriod = [[[(iCalDateTime *)[theEvent uniqueChildWithTag: @"dtstart"] timeZone] periodForDate: [theEvent startDate]] secondsOffsetFromGMT];
+  eventEndPeriod = [[[(iCalDateTime *)[theEvent uniqueChildWithTag: @"dtend"] timeZone] periodForDate: [theEvent startDate]] secondsOffsetFromGMT];
+
   while ((currentAttendee = [enumerator nextObject]))
     {
       currentUID = [currentAttendee uidInContext: context];
@@ -740,11 +745,11 @@
         // We MUST use the -uniqueChildWithTag method here because the event has been flattened, so its timezone has been
         // modified in SOGoAppointmentFolder: -fixupCycleRecord: ....
         rangeStartDate = [[fbInfo objectAtIndex: i] objectForKey: @"startDate"];
-        delta = [[rangeStartDate timeZoneDetail] timeZoneSecondsFromGMT] - [[[(iCalDateTime *)[theEvent uniqueChildWithTag: @"dtstart"] timeZone] periodForDate: [theEvent startDate]] secondsOffsetFromGMT];
+        delta = [[rangeStartDate timeZoneDetail] timeZoneSecondsFromGMT] - eventStartPeriod;
         rangeStartDate = [rangeStartDate dateByAddingYears: 0  months: 0  days: 0  hours: 0  minutes: 0  seconds: delta];
 
         rangeEndDate = [[fbInfo objectAtIndex: i] objectForKey: @"endDate"];
-        delta = [[rangeEndDate timeZoneDetail] timeZoneSecondsFromGMT] - [[[(iCalDateTime *)[theEvent uniqueChildWithTag: @"dtend"] timeZone] periodForDate: [theEvent endDate]] secondsOffsetFromGMT];
+        delta = [[rangeEndDate timeZoneDetail] timeZoneSecondsFromGMT] - eventEndPeriod;
         rangeEndDate = [rangeEndDate dateByAddingYears: 0  months: 0  days: 0  hours: 0  minutes: 0  seconds: delta];
 
         range = [NGCalendarDateRange calendarDateRangeWithStartDate: rangeStartDate