Set Comparison to Prior Period that Auto Adjusts Based on the Current Date Range

@aent22  may be not what you looking for  but below is possible where when you change time for range it auto adjust 

This is possible, and there are two steps that you need to do for this.

First, create a time period column that has a rolling date range. If you want the previous 7 days to your time period, set it up like this:

The second step is to set up the date range in your panel. I've got it set to the last 7 days, then I've also selected the two options at the bottom - rolling date range and make dates relative. The rolling date range will make sure it's always the last 7 days. The second option is the important one - making date ranges relative. What this does is it makes all of the date range columns in your panel relative to the date range. So, rather than being the last 7 days from today, it makes it the last 7 days from your date range.

So when you bring in dates, it looks like this:

You can see in the last screenshot, when I add my "last 7 days" date range, it makes it relative to the date in the panel and gives me the previous 7 days.

One thing I will call out about this is that the number of days in the comparison date range doesn't change. If you do the last 7 days in your purple date range, and then change your panel to 14 days, the purple column will stay at 7 days. But it will always give you the comparison to the first date in your panel date range.

As others have said, Adobe does allow for relative comparisons based on a selected date but it is locked to a set number of days (i.e. it is locked to 7 days, or whatever you set up in your date range definition), but there is no way to make a truly comparative date range reflecting both the selected dates and the span of the selected range.

However, you can do this in Excel with Report Builder. So depending on your needs, you may have to consider creating this report outside of Adobe.

To do this with Report Builder, instead of choosing any of the pre-defined date ranges, use "Dates from Cells", then have to and from cells set up for you or someone to input the date range, then in a hidden sheet (so that no one can break it) use Excel formulas to calculate the comparison to and from based on the inputted values.