You can achieve this by using the system macro/variables in the report file name, seen in the screenshot of the example below.
NCM > Jobs > Create/Edit "Config Change Report" > "Enter Notification Details".
If you have multiple pollers, make sure to choose a path that exists on each poller.
Then, try something similar to this, somewhere in the filename:
_${YYYY}-${MM}-${DD}_
This should allow you to save 1 file per day, without overwriting it. (Unless, of course, you run the job again, on the same day it had already run.)
I hope this helps you.
-Will