The point here is if you are sure that you have issue with only year 2014 and records pertaining to it then you can opt for field level routine.
Map the source field to this date infoobject-Rule type routine.
If Source_fields-date+0(2) = '14'.
Concatenate '20' Source_fields-date into Result.
Else.
Result = 'Technical name of the infoobject'.
Hope this gives an idea.
Try to implement this routine,if it gives syntax error then let me know.
Regards,
AL