Date Conversion yyddd to mm/dd/yyyy

Question

I have a structure that has the date stored in yyddd (Ordinal ISO 8601 format), I need to convert this to Gregorian Format or MM/dd/yyyy. I have tried and tried and have not come up with a good way to do this. does anyone have any hints? Example: 07117 = 04/27/2007 (ddd = DayOfYear) Thanks