Feature Request: Ability to compare time periods with unequal # of days

I’d love to have greater flexibility with date comparisons by selecting the “Custom” option.  Two different situations come to mind that I can’t do today in Heap UI (or at least can’t figure out how to do):

• Compare the entire month of July to June.  I can select July, but it forces me to choose a comparison time period that’s also 31 days.  We see a lot of activity on our sites the last day of the month, so if I’m including May 31st in with June (to make it 31 days), it’ll skew the results.
• Compare one promotion to another.  Let’s say one promotion ran for 5 days and another ran for 3 days.  Since they’re for varying lengths of time, it won’t allow me to select those time periods to compare.