Reopen the Calendar Bug
Feedback at yahoo.uservoice.com/forums/209451-us-groups/suggestions/4284757-the-calendar-software-on-yahoo-groups-is-full-of-b
was erroneously closed as "completed" when it is not fixed. Reminders are still announcing wrong dates. Please reopen that feedback to resume collecting comment cases and votes (it is ranked #3!)
Yahoo upgrades seem to always mess up this function. We've had issues with it with every major yahoo system change.