Last fall I mentioned a problem Windows mobile users had when syncing birthdays after installing Office 2007 SP2, where they birthdays changed to recur every 12 years.
This is now fixed:
Description of the Office Outlook 2007 hotfix package (outlook-x-none.msp): April 27, 2010
This hotfix covers a lot more than just this bug – including a number of calendar bugs. Its worth checking out if you use Outlook 2007.
Original tip: Tip 662: Recur every 12 years
Published April 29, 2010. Last updated on May 8, 2014.