diff --git a/calendar/base/public/calIItemBase.idl b/calendar/base/public/calIItemBase.idl
index 1da1482ac4d..0efb6365748 100644
--- a/calendar/base/public/calIItemBase.idl
+++ b/calendar/base/public/calIItemBase.idl
@@ -168,7 +168,7 @@ interface calIItemBase : nsISupports
    */
   const unsigned long ALARM_RELATED_END = 1;
 
-  // The last time this alarm was fired and acknowledged by the user
+  // The last time this alarm was fired and acknowledged by the user; coerced to UTC.
   attribute calIDateTime alarmLastAck;
 
   //
diff --git a/calendar/base/src/calAlarmService.js b/calendar/base/src/calAlarmService.js
index 4534824abe4..c646fe72d30 100644
--- a/calendar/base/src/calAlarmService.js
+++ b/calendar/base/src/calAlarmService.js
@@ -504,12 +504,6 @@ calAlarmService.prototype = {
     },
 
     removeAlarm: function cas_removeAlarm(aItem) {
-        // If the item has no alarm start date, then it was never added so don't
-        // remove it.
-        if (!this.getAlarmDate(aItem)) {
-            return;
-        }
-
         // make sure already fired alarms are purged out of the alarm window:
         this.notifyObservers("onRemoveAlarmsByItem", [aItem]);
         for each (var timer in this.removeTimers(aItem)) {
diff --git a/calendar/base/src/calEvent.js b/calendar/base/src/calEvent.js
index 8fa37c2b3fb..eb81038a255 100644
--- a/calendar/base/src/calEvent.js
+++ b/calendar/base/src/calEvent.js
@@ -133,7 +133,7 @@ calEvent.prototype = {
     { cal: "DTEND", ics: "endTime" }],
 
     set icalString(value) {
-        this.icalComponent = icalFromString(value);
+        this.icalComponent = getIcsService().parseICS(value, null);
     },
 
     get icalString() {
diff --git a/calendar/base/src/calItemBase.js b/calendar/base/src/calItemBase.js
index 17cc099b833..5f069003607 100644
--- a/calendar/base/src/calItemBase.js
+++ b/calendar/base/src/calItemBase.js
@@ -173,9 +173,9 @@ calItemBase.prototype = {
 
         if (this.alarmOffset) {
             this.alarmOffset.makeImmutable();
-            if (this.alarmLastAck) {
-                this.alarmLastAck.makeImmutable();
-            }
+        }
+        if (this.alarmLastAck) {
+            this.alarmLastAck.makeImmutable();
         }
 
         this.ensureNotDirty();
@@ -269,14 +269,14 @@ calItemBase.prototype = {
         // Clone any alarm info that exists, set it to null if it doesn't
         if (this.alarmOffset) {
             m.alarmOffset = this.alarmOffset.clone();
-            if (this.alarmLastAck) {
-                m.alarmLastAck = this.alarmLastAck.clone();
-            } else {
-                m.alarmLastAck = null;
-            }
         } else {
             m.alarmOffset = null;
         }
+        if (this.alarmLastAck) {
+            m.alarmLastAck = this.alarmLastAck.clone();
+        } else {
+            m.alarmLastAck = null;
+        }
         m.alarmRelated = this.alarmRelated;
 
         return m;
@@ -295,6 +295,19 @@ calItemBase.prototype = {
         return (this.mAlarmOffset = aValue);
     },
 
+    mAlarmLastAck: null,
+    get alarmLastAck cib_get_alarmLastAck() {
+        return this.mAlarmLastAck;
+    },
+
+    set alarmLastAck cib_set_alarmLastAck(aValue) {
+        this.modify();
+        if (aValue && !aValue.timezone.isUTC) {
+            aValue = aValue.getInTimezone(UTC());
+        }
+        return (this.mAlarmLastAck = aValue);
+    },
+
     get lastModifiedTime() {
         this.ensureNotDirty();
         return this.getProperty("LAST-MODIFIED");
@@ -625,18 +638,17 @@ calItemBase.prototype = {
             else
                 this.alarmRelated = Components.interfaces.calIItemBase.ALARM_RELATED_START;
 
-            var lastAck = alarmComp.getFirstProperty("X-MOZ-LASTACK");
-            if (lastAck) {
-                var lastAckTime = Components.classes["@mozilla.org/calendar/datetime;1"]
-                                            .createInstance(Components.interfaces.calIDateTime);
-                lastAckTime.icalString = lastAck.valueAsIcalString;
-                this.alarmLastAck = lastAckTime;
-            }
-
             var email = alarmComp.getFirstProperty("X-EMAILADDRESS");
             if (email)
                 this.setProperty("alarmEmailAddress", email.value);
         }
+
+        var lastAck = icalcomp.getFirstProperty("X-MOZ-LASTACK");
+        if (lastAck) {
+            var lastAckTime = createDateTime();
+            lastAckTime.icalString = lastAck.value;
+            this.alarmLastAck = lastAckTime;
+        }
     },
 
     importUnpromotedProperties: function (icalcomp, promoted) {
@@ -715,12 +727,6 @@ calItemBase.prototype = {
 
             alarmComp.addProperty(triggerProp);
 
-            if (this.alarmLastAck) {
-                var lastAck = icssvc.createIcalProperty("X-MOZ-LASTACK");
-                lastAck.valueAsIcalString = this.alarmLastAck.icalString;
-                alarmComp.addProperty(lastAck);
-            }
-
             // We don't use this, but the ics-spec requires it
             var descProp = icssvc.createIcalProperty("DESCRIPTION");
             descProp.value = "Mozilla Alarm: "+ this.title;
@@ -740,6 +746,13 @@ calItemBase.prototype = {
 
             icalcomp.addSubcomponent(alarmComp);
         }
+
+        if (this.alarmLastAck) {
+            var lastAck = getIcsService().createIcalProperty("X-MOZ-LASTACK");
+            // - should we further ensure that those are UTC or rely on calAlarmService doing so?
+            lastAck.value = this.alarmLastAck.icalString;
+            icalcomp.addProperty(lastAck);
+        }
     },
     
     getOccurrencesBetween: function(aStartDate, aEndDate, aCount) {
@@ -777,17 +790,3 @@ function makeMemberAttr(ctor, varname, dflt, attr, asProperty)
     ctor.prototype.__defineGetter__(attr, getter);
     ctor.prototype.__defineSetter__(attr, setter);
 }
-
-//
-// helper functions
-//
-
-function icalFromString(str)
-{
-    return getIcsService().parseICS(str, null);
-}
-
-function icalProp(kind)
-{
-    return getIcsService().createIcalProperty(kind);
-}
diff --git a/calendar/base/src/calTodo.js b/calendar/base/src/calTodo.js
index 390739d2cf5..fc47373505e 100644
--- a/calendar/base/src/calTodo.js
+++ b/calendar/base/src/calTodo.js
@@ -161,7 +161,7 @@ calTodo.prototype = {
     { cal: "COMPLETED", ics: "completedTime" }],
 
     set icalString(value) {
-        this.icalComponent = icalFromString(value);
+        this.icalComponent = getIcsService().parseICS(value, null);
     },
 
     get icalString() {
diff --git a/calendar/providers/storage/calStorageCalendar.js b/calendar/providers/storage/calStorageCalendar.js
index 6481e524a4b..ebae5304c89 100644
--- a/calendar/providers/storage/calStorageCalendar.js
+++ b/calendar/providers/storage/calStorageCalendar.js
@@ -1535,10 +1535,10 @@ calStorageCalendar.prototype = {
 
             item.alarmOffset = duration;
             item.alarmRelated = row.alarm_related;
-            if (row.alarm_last_ack) {
-                // alarm acks are always in utc
-                item.alarmLastAck = newDateTime(row.alarm_last_ack, "UTC");
-            }
+        }
+        if (row.alarm_last_ack) {
+            // alarm acks are always in utc
+            item.alarmLastAck = newDateTime(row.alarm_last_ack, "UTC");
         }
 
         if (row.recurrence_id)
@@ -1998,9 +1998,9 @@ calStorageCalendar.prototype = {
         if (item.alarmOffset) {
             ip.alarm_offset = item.alarmOffset.inSeconds;
             ip.alarm_related = item.alarmRelated;
-            if (item.alarmLastAck) {
-                ip.alarm_last_ack = item.alarmLastAck.nativeTime;
-            }
+        }
+        if (item.alarmLastAck) {
+            ip.alarm_last_ack = item.alarmLastAck.nativeTime;
         }
     },