The calendar archive widget doesn't display the correct start date for the week when viewing individual posts. It is correct on the main/home page. I have tried multiple themes and even the default theme.
Looks fine: http://blog.jolexa.net
Looks broken: http://blog.jolexa.net/2009/11/22/buggy-mtrr-on-acer-aspire-one-zg5/
(It is the first widget on the right)