It is very useful to be able to quickly gain insight on how your project is performing compared to recently, say on a weekly basis.
You can quickly add a comparison period in the report builder. Click the cog in your report and click edit.
Scroll down to the date picker. You'll notice at the bottom there are several options for comparison periods.
Here we have selected Last Week as the date range and Week-on-Week, and Month-On-Month as a comparison period. Next to the period you can see the date ranges.
These comparisons are the simplest when the periods match, e.g. Last Week WoW period will be a month starting a week early, but you can choose any combination, e.g. this week a month ago, one month commencing a week earlier, or this month last year.
You can even choose a custom period (and save it if you wish) and compare it to the previous period by clicking Prev Period e.g. Last 10 days and 10 days prior.
You can even customise the previous period and technically compare any two periods!