anchor.diff:  (defparameter +rfc-1123-format+
     ;; Sun, 06 Nov 1994 08:49:37 GMT
     '(:short-weekday ", " (:day 2) #\space :short-month #\space (:year 4) #\space
  -    (:hour 2) #\: (:min 2) #\: (:sec 2) #\space :timezone)
  -  "Please note that you should use the +GMT-ZONE+ timezone to format a proper RFC 1123 timestring. See the RFC for the details about the possible values of the timezone field.")
  +    (:hour 2) #\: (:min 2) #\: (:sec 2) #\space :gmt-offset-hhmm)
  +  "See the RFC 1123 for the details about the possible values of the timezone field.")
   
   (defparameter +iso-week-date-format+
     ;; 2009-W53-5
  
positive.code:   :AMPM              am/pm marker in lowercase
    :GMT-OFFSET        the gmt-offset of the time, in +00:00 form
    :GMT-OFFSET-OR-Z   like :GMT-OFFSET, but is Z when UTC
    :TIMEZONE          timezone abbrevation for the time
  
  Elements marked by * can be placed in a list in the form: \(:keyword padding &optional \(padchar #\0))
  
negative.code:       (write-string result (if (eq t destination) *standard-output* destination)))
      result))
  
  (defun format-rfc1123-timestring (destination timestamp &key
                                    (timezone *default-timezone*))
    (format-timestring destination timestamp
                       :format +rfc-1123-format+
                       :timezone timezone))
  
  (defun to-rfc1123-timestring (timestamp)
    (format-rfc1123-timestring nil timestamp))
  