The week reset is covered in comments above, we reset at 00:00 UTC, now for the 10 rep difference:
The week/month/etc changes are the net change in that period (e.g.
endRep - startRep), so why doesn't this seem to match your rep report?
After you edited your answer here someone reversed their upvote on it (on 2011-03-16), meaning you lost that 10 rep. So for the week, you lost 10, brining your week change down to 65.
Update: In the next build "today" will behave the same as the other intervals, like week, month, quarter and year. Every interval now means:
"How much did your rep change from the beginning of [the X"
To be as explicit as possible:
- today - "How much did my rep change from the beginning of today?"
- week - "How much did my rep change from the beginning of the week?"
- month - "How much did my rep change from the beginning of the month?"
- quarter - "How much did my rep change from the beginning of the quarter?"
- year - "How much did my rep change from the beginning of the year?"
These meanings apply everywhere: currently the user popup and the
For example (related to this question):
If you got 10 upvotes for 100 rep today, but someone reversed an upvote from months ago (but they did so today) then you would see +90 as the change today, since from the beginning of the day your total rep went up 90.
You should only see this mis-match from the "votes today" on your reputation profile tab when someone reverses their vote (due to an edit, etc). If this is too much to bear, you can recalc your reputation which will sync up all history and not show that previous increase (or the corresponding decrease from the reversal) ever happened.