How to create a monthly recurrence ?

To create a monthlyrecurrence : 

Repeats Monthly In this example, from  08:00 to 10:00, a contact is on duty.  
Intervall between two periods   If 1 intervall between 2 periods, it means that recurrence is fixed every month. If 2 invervalls between 2 periods, the recurrence is fixed every 2 months, etc.  
Starts on
  Stat of the recurrence is fixed at the creation of the event. It is the date on which the recurrence starts.  
Ends  After n recurrence    It is possible to choose the wished number of recurrences.  
   On date It is possible to select a date on which the recurrence ends.  


In the above example, the recurrences will appear like that in the Calendar (all 10 of the month, during 6 months, from 08:00 to 10:00, a person is on duty) :