Hi Yoni,
It works now.
I just changed the calendar_backend to database.
But I have another error, or shall I say a bug.
When I try to save an event in the calendar, let's just say the event is from 5:00 PM TO 10:00 PM. After hitting save, the outcome is not the same as I expected. Instead of 5:00 PM to 10:00 PM, 3:00 AM to 6:00 AM.