diff --git a/SOPE/NGCards/ChangeLog b/SOPE/NGCards/ChangeLog
index a2fec6384..b74626387 100644
--- a/SOPE/NGCards/ChangeLog
+++ b/SOPE/NGCards/ChangeLog
@@ -1,3 +1,9 @@
+2010-03-09  Wolfgang Sourdeau  <wsourdeau@inverse.ca>
+
+	* iCalTimeZonePeriod.m (_occurenceForDate:byRRule:): fixed
+	computing of timezone switch dates, which were offset by one week
+	too early.
+
 2010-01-06  Wolfgang Sourdeau  <wsourdeau@inverse.ca>
 
 	* iCalDateTime.m (-setTimeZone:): don't modify the date in case of
diff --git a/SOPE/NGCards/iCalTimeZonePeriod.m b/SOPE/NGCards/iCalTimeZonePeriod.m
index 855f7c8a2..f1f7a0a04 100644
--- a/SOPE/NGCards/iCalTimeZonePeriod.m
+++ b/SOPE/NGCards/iCalTimeZonePeriod.m
@@ -105,6 +105,8 @@
 			   dateTime];
 }
 
+/* This method returns the date corresponding for to the start of the period
+   in the year of the reference date. */
 - (NSCalendarDate *) _occurenceForDate: (NSCalendarDate *) refDate
 			       byRRule: (iCalRecurrenceRule *) rrule
 {
@@ -132,12 +134,7 @@
 		     second: -[self _secondsOfOffset: @"tzoffsetfrom"]];
 
   dateDayOfWeek = [tmpDate dayOfWeek];
-
-  if (pos > 0)
-    offset = (dayOfWeek - dateDayOfWeek) + ((pos - 1) * 7);
-  else
-    offset = (dayOfWeek - dateDayOfWeek) + (pos * 7);
-
+  offset = (dayOfWeek - dateDayOfWeek) + (pos * 7);
   tmpDate = [tmpDate addYear: 0 month: 0 day: offset
 		     hour: 0 minute: 0 second: 0];