iPhone4 calendar repetitive date issue

The calendar in my wife's iPhone4 is displaying all future repetitive events on the wrong date, specifically repetitive dates such as birthdates. They are on the correct date in 2012 and are directed to repeat yearly but in 2013 & 2014 they appear one day later, for instance birthdays showing up on January 1st are now appearing on January 2nd.

Additional info - she syncs to her Outlook Calendar. Her Outlook calendar has all of this info in the correct date for future years, but it doesn't sync over properly. However, if you put a test entry in the calendar, the new info syncs over to the correct date, but the old info does not get corrected.

We have not yet upgraded to iOS7

Any help is greatly appreciated!