diff --git a/mozilla/calendar/base/content/calendar-month-view.xml b/mozilla/calendar/base/content/calendar-month-view.xml
index 2c52f5538b7..79d8eb15d20 100644
--- a/mozilla/calendar/base/content/calendar-month-view.xml
+++ b/mozilla/calendar/base/content/calendar-month-view.xml
@@ -25,6 +25,7 @@
    -   Stefan Sitter <ssitter@googlemail.com>
    -   Clint Talbert <cmtalbert@myfastmail.com>
    -   Michael Büttner <michael.buettner@sun.com>
+   -   Philipp Kewisch <mozilla@kewis.ch>
    -
    - Alternatively, the contents of this file may be used under the terms of
    - either the GNU General Public License Version 2 or later (the "GPL"), or
@@ -638,6 +639,21 @@
            var beginMove = item.startDate.clone();
            beginMove.isDate = true;
            var duration = boxDate.subtractDate(beginMove);
+           
+           // Since both boxDate and beginMove are dates (note datetimes),
+           // subtractDate will only give us a non-zero number of hours on DST
+           // changes. While strictly speaking, subtractDate's behavior is 
+           // correct, we need to move the event a discrete number of days here.
+           // There is no need for normalization here, since addDuration does 
+           // the job for us.
+           if (duration.hours == 23) {
+             // entering DST
+             duration.hours++;
+           } else if (duration.hours == 1) {
+             // leaving DST
+             duration.hours--;
+           }
+
            newStart = item.startDate.clone();
            newStart.addDuration(duration);
            newStart.normalize();
diff --git a/mozilla/calendar/base/content/calendar-multiday-view.xml b/mozilla/calendar/base/content/calendar-multiday-view.xml
index 0022f956bff..796e640bed0 100644
--- a/mozilla/calendar/base/content/calendar-multiday-view.xml
+++ b/mozilla/calendar/base/content/calendar-multiday-view.xml
@@ -25,6 +25,7 @@
    -   Thomas Benisch <thomas.benisch@sun.com>
    -   Dan Mosedale <dan.mosedale@oracle.com>
    -   Michael Büttner <michael.buettner@sun.com>
+   -   Philipp Kewisch <mozilla@kewis.ch>
    -
    - Alternatively, the contents of this file may be used under the terms of
    - either the GNU General Public License Version 2 or later (the "GPL"), or
@@ -1124,6 +1125,23 @@
               // Figure out how much the event moved.
               var duration = col.mDate.subtractDate(dragState.origDate);
               var minutes = dragState.startMin - dragState.origMin;
+
+              // Since both boxDate and beginMove are dates (note datetimes),
+              // subtractDate will only give us a non-zero number of hours on 
+              // DST changes. While strictly speaking, subtractDate's behavior
+              // is correct, we need to move the event a discrete number of
+              // days here. There is no need for normalization here, since
+              // addDuration does the job for us. Also note, the duration used
+              // here is only used to move over multiple days. Moving on the 
+              // same day uses the minutes from the dragState.
+              if (duration.hours == 23) {
+                  // entering DST
+                  duration.hours++;
+              } else if (duration.hours == 1) {
+                  // leaving DST
+                  duration.hours--;
+              }
+
               if (duration.isNegative) {
                   // Adding negative minutes to a negative duration makes the
                   // duration more positive, but we want more negative, and