yes, having to click that clock is annoying, but you have to have a time for appointments.
1) you can use an Initial Value of CURRENT_TIMESTAMP in the BO
2) On an Appointment, I set the END_TIME = to 60 minutes after the START_TIME... this way the user doesn't have to mess with it and it will work for the Calendar.
Its in an Update Rule that has to be checked DYNAMIC.
if Appointment.StartTime WAS CHANGED THEN Appointment.EndTime=TIME_ADD(Appointment.StartTime,1)