I was going to ask if it was a calendar week or last 7 days but then I read the post again.

I suggest a calendar week, because like the all-time ranking, it will be difficult to top the highest ranked because he has been able to play probably most games, too. I mean, it is easier to maintain number 1 position than to start every week from scratch, at least that's how I feel. So by measuring every calendar week games, we would probably have more different number 1's.