anchor.diff:                                (parse-integer datestr :start (1+ pos))))))))
                 0)))
       (with-decoded-timestamp (:nsec nsec :sec sec :minute minute :hour hour)
  -        (parse-timestring (subseq intervalstr (or date-time-separator-index 0)))
  -      (encode-interval :nsec nsec :sec (+ extra-sec sec) :minute minute :hour hour))))
  -
  -(defun format-interval (interval &key (omit-date-part-p nil) (omit-time-part-p nil)
  +        (parse-timestring (subseq durationstr (or date-time-separator-index 0)))
  +      (encode-duration :nsec nsec :sec (+ extra-sec sec) :minute minute :hour hour))))
  +
  +(defun format-duration (duration &key (omit-date-part-p nil) (omit-time-part-p nil)
                           (date-elements (if omit-date-part-p 0 2)) (time-elements (if omit-time-part-p 0 4))
                           (date-separator #\-) (time-separator #\:) (date-time-separator #\T))
     (multiple-value-bind (nsec usec msec second minute hour day week)
  -      (decode-interval interval)
  +      (decode-duration duration)
       (with-output-to-string (str nil :element-type 'base-char)
         (when (zerop week)
           (decf date-elements)
  
positive.code: 
  (defun timestamp- (time-a time-b)
    "Returns the difference between TIME-A and TIME-B in seconds"
    (setf time-a (adjust-timestamp time-a (set :timezone (timezone-of time-b))))
    (multiple-value-bind (sec-a day-a)
        (adjust-to-timezone time-a (timezone-of time-b))
      (let ((nsec (- (nsec-of time-a) (nsec-of time-b)))
            (second (- sec-a (sec-of time-b)))
            (day (- day-a (day-of time-b))))
        (when (minusp nsec)
          (decf second)
          (incf nsec 1000000000))
        (when (minusp second)
          (decf day)
          (incf second +seconds-per-day+))
        (encode-interval :nsec nsec :sec second :day day))))
  
  (defun timestamp+ (time seconds)
    "Returns a new TIMESTAMP containing the sum of TIME and SECONDS"
  
negative.code:            #:days-in-month
             #:timestamp-
             #:timestamp+
             #:duration
             #:decode-duration
             #:parse-duration
             #:format-duration
             #:maximize-time-part
             #:minimize-time-part
             #:first-day-of-year
  