Formula for Date from text

I would use a custom function for this.

Function GetDate(ByVal EBT as string) as Date

   ' get the year
   MyYear = CInt("20"+Mid(EBT,4,2))

   ' get the week
   MyWeek = CInt(Mid(EBT,6,2))

   ' calc days
   DaysInYear = 7 * MyWeek

   GetDate = DateSerial(MyYear,1,1)
   GetDate = DateAdd("d", DaysInYear, GetDate)

End Function

If the encoded date is in cell A1, then in cell B1 you enter the formula =GetDate(A1)