The problem (if it's the same as mine!) is that when you view the outlook calendar, the selected date is not today. In my case it is5 weeks ago (25th Sept instead of the 31 Oct).
Found the cause of this on http://www.slipstick.com/calendar/wrongdate.htm. Basically it's because outlook always shows the 1st day of the current month and because the month view in outlook displays 5 weeks it can cause this behavior. Follow the link for more details
The upshot is I couldn't find a cure but it will only happen a few months of the year and will sort itself out next month.