diff --git a/app/models/calentry.rb b/app/models/calentry.rb
index c4138b0..e8f8ef4 100644
--- a/app/models/calentry.rb
+++ b/app/models/calentry.rb
@@ -39,7 +39,7 @@ validate do |entry|
     start.to_date
   end
   def dauer
-    self.start-self.ende
+    (self.ende-self.start)/3600
   end
   def dauer=(dauer)
     self.ende=self.start+dauer.to_i.hours