Excellent! Looks like it is now working. Can you tell me if there is a setting I missed for adding the submit button? I didn't realize the submit button needed to be custom coded or it wouldn't appear. I thought it would just be there as part of the filter when I chose the field.
Now that I see how to do it, I can easily duplicate this in other views by copying and pasting how you did it. But I wouldn't have known the custom code that was needed here.
OK, I've added the same date range filter to all our views. It looks like it is working properly on all of them! Thanks hugely again for getting us past this one. This was a big one to see it completed. Very happy with getting this one done. I'll mark this thread as resolved now.