change default lookback period for report, aggregate and log to 7 days

[kvnloughead]

This attempts to resolve this issue. By default, the report and aggregate commands give the previous 8 days, and not 7 as one would expect. I also changed the default for the log command for consistency.

This is my first time contributing to something like this, so apologies if I haven't done everything correctly. In particular I'm not sure what is meant by "The pull request should include tests." I rantox, and it passed for 3.6 and 3.9 (the only versions I have installed), but how do I "include" the tests?