Changed some properties

Calendar/CalendarEvent.py

@@ -1,8 +1,8 @@
 class CalendarEvent (object):
     """Defines a calendar event, independent of any implementation"""
     def __init__ (self):
-        self.datetime = None
-        self.duration = None
+        self.begin_datetime = None
+        self.end_datetime = None
 
         self.title = None
         self.description = None