"I also don't believe that stone circles were necessary for people to *know* about the time of year. It is far too easy to know the time of the year by crossing out days in a homemade calendar."
I agree. You can cross out days on a home made calendar, or you can simply look at where the sun goes down. That tells you where you are in the year to an accuracy of a single day.
With such a perfect and accurate means of knowing the time of year available to every farmer I can't help thinking that stone circles and interest in the moon both owed less to practical need and more to priestly and ritual showing off.