Here is the IsConflict function from EventsController.vb. Look at the highlighted line.

Public Function IsConflict(ByVal objEvent As EventInfo) As Boolean
 Dim oEventEvent As EventInfo
 Dim newBeginDateTime As DateTime
 Dim newEndDateTime As DateTime
 Dim calBeginDateTime As DateTime
 Dim calEndDateTime As DateTime
 newBeginDateTime = Convert.ToDateTime(objEvent.EventDateBegin.ToShortDateString().ToString() + " " + objEvent.EventTimeBegin.TimeOfDay().ToString())
 newEndDateTime = newBeginDateTime.AddMinutes(CType(objEvent.Duration, Double))
 For Each oEventEvent In EventEvents
  calBeginDateTime = Convert.ToDateTime(oEventEvent.EventDateBegin.ToShortDateString + " " + oEventEvent.EventTimeBegin.TimeOfDay().ToString())
  calEndDateTime = calBeginDateTime.AddMinutes(CType(oEventEvent.Duration, Double))
  If newBeginDateTime >= calBeginDateTime And newBeginDateTime <= calBeginDateTime And _
   (oEventEvent.EventID <> objEvent.EventID) Then
    Return True
  End If
  Next
 Return False
End Function

This line can be rewritten as "IF newBeginDateTime = calBeginDateTime". I don't think this is what the original author intended. I believe the correct statement should be:

If newBeginDateTime <= calEndDateTime And newEndDateTime >= calBeginDateTime And _
  (oEventEvent.EventID <> objEvent.EventID) Then

It should also be noted that the conflict detector as written will only check the first date in a recurring event.

Questions and comments welcome.

Dan