Reports with Month-end rather that Month-start

[km22]

Hi Gnucash community,

I want to start editing -- and eventually creating -- my own reports and
figures.  I think one place for me to start learning is by playing with
some existing report settings -- such as the report date functionality. 
Currently when I run a report with a "monthly" period I get the 1st day
of each month.  How could I edit the report settings so I get the last
day of each month instead?  (I am a Windows 7 user if that makes a
difference on where to find/edit files.)

Thanks,

Ken