Date math in NACHA rtf for output to etext file

We are using IBYDE_N1US_en.rtf template and have modified it to our bank's specs.  We are using position 70 in record 5 as our "Settlement" date.  Our policy is to make that date 1 day past the payment date.  The following code has worked fine until May 31, 2012 when the output should have been 120601 (June 1, 2012.)  However it is 201205 in the output.  The code works fine in Toad or sqlplus.  What's wrong with this: DECODE(substr(to_char(OutboundPayment/PaymentDate+1,’DY’),1,1),’S’, OutboundPayment/PaymentDate+3, OutboundPayment/PaymentDate+1)?  Thanks.