As for the January Release you can now use date ranges in segments
including rolling date ranges. This should let you do what you are
looking for. Just create a segment for previous month or previous year
and add it to the derived metric. Also as a shortcut in Analysis
Workspace you right click on any metric column and add a time comparison
column. This will let you do the same thing as well. This doesn't
totally solve your use case becuase it isn't based of off the report
date but it is based o...