"7. 7.A week (or a month) always begins and ends in the same year."
Not sure what the (or a month) is doing there. I'm pretty sure the end of december is the end of the year and the beginning of January is the beginning of the year. A month can't span multiple years...can it?
You are right. I said "a month" but I meant something more like "a period of 28 days" or "a month-long period." I'll think about how to word this more clearly.
