Cannot group items by Last Activity Date for Reports/Charts

Cannot group items by Last Activity Date for Reports/Charts

When I try to graph usage of Accounts, Leads, etc. by Last Activity Date, I get a result where each item is separately presented.

The reason? While it's called Last Activity DATE, when creating the underlying report, what's available is Last Available TIME  (see below) , so no two items have the same time to the second and grouping by date is meaningless .

I tried creating a Date-only field and cloning the LAD, but couldn't get it to work.

Is there a field available for reporting that can support this? Otherwise, is tracking on LAD impossible?

Thanks in advance.
Eriel Ramos-Pizarro