In version 1.8, CurrentKey Stats‘ “30-days” view gets some love. Now, as your stats pile up, you can see how each of the last four weeks measure up, with a total time spent number and downloadable report. [App Store link]
These are formal weekly (7-day) spans, and you can tell the app if you prefer that they start on Sunday or Monday.
Remember: you can filter these stats by Specific Room. So, if you wanted to see how long you spent in a space you called “Client #1” or “Recreation”, just toggle the Specific Room option in the bottom bar, and viola – everything updates accordingly. It’s slick!