I currently run a monthly report that summarises request resolutions by each of our support groups during the previous calendar month.  This works well, but now that we've had SD+ for some time,  I would like to create a trend report to compare this information across several months.

Specifically, I'd like to create a stacked bar chart, stacked on resolving group, where each bar relates to tickets resolved or closed in a single calendar month.  My problem is in getting those resolution/closure dates grouped together into calendar months.  Is there any possibility to get this report created as I envisage?