I've changed the active players query to consider experience earned, rather than trophies, as I suspect it is a better way to quantify activity balanced against difficulty (as discussed in this thread: http://forums.proletariat.com/t/about-the-leaderboards/3267/16). The column headers on the page are an accurate reflection of the data.
Yes, you're correct that the current stat seems to be only tracking slightly more than six days of activity. That has to do with how we bucket and calculate Day 7 experience. When you gain experience (either player experience or guild experience), we take the amount you're gaining (considered before we apply the level cap) and put it into a bucket for today, based on UTC dates. We keep the last seven days worth of buckets. Whenever we save the player (or guild) we write out the seven day experience (xpD7) for today by summing all the values for the last seven days (including today), and we also write the values for the next six days (by decrementing the number appropriately for each subsequent day).
We chose this design because it means that as soon as a player disconnects we know their valid xpD7 at any time for that day or the next six days. We don't have to run any nighty code to compute those numbers, and it handles those players not playing for a day or two at a time.
Currently we can only query the value for today (which is changing as people play) or the future, and so when we run the query to generate the top-100 page, we're using xpD7 from today, and we're doing it right after UTC midnight, so the day is only a few minutes old. So you're seeing six full days and a seventh day with only a few minutes of activity. I might investigate running the top-100 query at the end of the day, so that it is a more complete picture. But ultimately I'd like to invest the time doing a real fix: we should store eight days worth of data so that we could compute an immutable xpD7 value for yesterday. Then we would use the immutable value for yesterday to rank players, it would be a full seven days worth of activity, and it wouldn't matter when we ran the query.
The fact that the number is changing while the query was running was the source of the sorting problems that once plagued this page. I've changed how the final ranking works, so you should see a stable rank now.
I'll be sure to post again if we make other changes to how this works. Also, I really like the idea of putting xpD7 or gXPD7 into the game UI somewhere, but I honestly don't know where we would surface this information. Something to think about!