I'm not sure I understand your RSS feed question. If you want to create date stamps in the proper RSS / RFC822 format, I think what you want to use is SRFI-19: http://srfi.schemers.org/srfi-19/srfi-19.html
The require statement loads SRFI-19 into MzScheme. The string with ~'s specifies the output format.
Instead of (current-date), you can use (make-time time-utc 0 1207956960), using whatever seconds since 1970 time you want in place of 1207956960. There maybe needs to be a time zone correction in there.