anchor.diff:               ;; "YYDDD"
                (5 ;; c.f. RFC 3339, 3. Two Digit Years, last item
                   (when (<= #.(char-code #\:) (char-code (char date 0)))
  -                  (setf (char date 0)
  -                        (digit-char (- (char-code (char date 0)) #.(char-code #\:)))))
  -
  +                  (let ((broken-two-digit-year (subseq date 0 2)))
  +                    (setf (char date 0)
  +                          (digit-char (- (char-code (char date 0)) #.(char-code #\:))))
  +                    (warn "Broken two-digit year ~S was parsed as \"~S\". (c.f. RFC 3339, 3.)"
  +                          broken-two-digit-year (+ 2000 (parse-integer date :start 0 :end 2)))))
                   (parse-year (+ 2000 (parse-integer date :start 0 :end 2)))
                   (parse-days (subseq date 2)))
                ;; "YYMMDD"
  
positive.code:                            (progn
                               ;; c.f. RFC 3339, 3. Two Digit Years, last item
                               (when (<= #.(char-code #\:) (char-code (char token 0)))
                                 (setf (char token 0)
                                       (digit-char (- (char-code (char token 0)) #.(char-code #\:)))))
  
                               (parse-year (+ 2000 (parse-integer token)))
                               (setf year-parsed? t))))
                      ;; "YYYY", "YYYYYY"
  
negative.code: 
        (when (equal 0 leap-year?)
          (let ((this-year (nth-value 5 (get-decoded-time))))
            (warn "YEAR was not detected in ~S as RFC822-Genus. YEAR was supplemented with this year, \"~S\"."
                  date-time-string this-year)
            (parse-year this-year)))
  
  