Calendar setup

In order for depreciation to run, I understand that the current Fiscal year must be defined as well as the next Fiscal Year.  However, in the documentation it states that at the end of each Fiscal year, the depreciation program automatically generates the dates for the following fiscal year and calendars. 

First, how can it generate the next Fiscal year, when it already had to be defined for depreciation to run in the current year? 

Second, we use a 4-4-5 closing schedule so our ending dates fluctuate from month to month. Will the system automatically generate the calendar as well?  Is it better to let the system generate the periods and then go in and update them or is it better to just define them myself?  I am also understanding that the system will automatically generate the Prorate calendars.