Wow, there is a bug there, I had never noticed it. The day selectors were working correctly only if you don't change the month with the month selector, after changing the month the date selectors behave unexpectedly. I just fixed it in my copy so it will be fixed in the next release.
Not sure what you mean by workaround is type the date unless you are using and older version of mojoPortal. In the latest version its all done in ajax so it doesn't change the url when you navigate with the calendar. In older versions of mojoPortal we did pass the date in the url.
Thanks for the bug report.