Quote Originally Posted by MarvinP View Post
I guess that's not how I read the problem. I think s/he wants my answer and just didn't know how to ask it.

I'll keep scratching my brain to see if the On until Off then On again solution comes to mind.
What happens if there are 3 dates in the same month? On, Off and On all in the same month. I still like my answer.
In kwjoh's post and attached example, it shows

start 5/23/07
end 9/20/07

In the example results, May, September, and all the months in between are marked as 1. That's a pretty stark example. My interpretation is "Mark any month which contains at least one day that falls within any of the start/end intervals."

Hopefully kwjoh will come back to visit and confirm.