Why do Calendar reports defaults to month when it loads ?
This is a OOB behaviour and it is not configurable.
Note:By default, calendar reports open to the current month unless there is no record for that month. If there is no record for that month, the calendar reports open to the next month that contains a record.
1> Create a new Calendar report.
2> When you run it always defaults to month view.
3>Change the setting to week and save the report.
4> Reload the report it will default to monthly.