Currently, the Finish Date variable is only sorted by the day on Table views for Reports (and graphs). To make the reports more useful in terms of numbers/budgeting, it would make sense to have the ability of aggregating the values into the Month/Year values. Example:
Project 1 Complete - 04/01/18
Project 2 Complete - 04/26/18
Project 3 Complete - 04/30/18
Projects completed in April - 3 (in a report format, table or graph)
Projects completed in 2018 - 3 (in a report format, table or graph)