diff --git a/src/calanonsync/ews.go b/src/calanonsync/ews.go
index 7002687..b67c113 100644
--- a/src/calanonsync/ews.go
+++ b/src/calanonsync/ews.go
@@ -2,6 +2,8 @@ package main
 
 import (
 	"bytes"
+	"crypto/md5"
+	"encoding/hex"
 	"encoding/xml"
 	"fmt"
 	"io"
@@ -18,10 +20,20 @@ type FolderId struct {
 }
 
 type CalendarItem struct {
-	Subject string
-	UID     string
-	Start   time.Time
-	End     time.Time
+	Subject          string
+	UID              string
+	Start            time.Time
+	End              time.Time
+	RecurrenceId     string
+	Sensitivity      string
+	CalendarItemType string
+}
+
+func (ci CalendarItem) Hash() string {
+	h := md5.New()
+	h.Write([]byte(ci.UID))
+	h.Write([]byte(ci.RecurrenceId))
+	return strings.ToUpper(hex.EncodeToString(h.Sum(nil)))
 }
 
 type EWSCalendar struct {