“this month” highlighted with “today”
When either "Today" or "This Month" is selected, both sub-tabs are highlighted.
Judging by the nature of today's date (June 1st), the reason both "Today" and "This Month" are highlighted is because they are the same span of time. Each sub-tab in Recent Activity doesn't seem to be a separate page, but just different evaluations of the values for
"This Month" cannot span past the current day; only time which has already existed can be recorded. So in this case, all "This Month" covers is "6/1/2010 - 6/1/2010", which is also what "Today" evaluates to. I would imagine that likewise, "This Week" will be highlighted alongside "Today" at the start of every week, since that too only evaluates as far as time has occurred.