anchor.diff:    "Given a number of days, returns the number of years and the remaining days in that year."
     (let ((remaining-days days))
       (multiple-value-bind (400-years remaining-days)
  -        (floor remaining-days 146097)
  -      (let* ((100-years (min 3 (floor remaining-days 36524)))
  -             (remaining-days (- remaining-days (* 100-years 36524))))
  +        (floor remaining-days #.(years-to-days 400))
  +      (let* ((100-years (min (floor remaining-days #.(years-to-days 100)) 3))
  +             (remaining-days (- remaining-days
  +                                (* 100-years #.(years-to-days 100)))))
           (multiple-value-bind (4-years remaining-days)
  -            (floor remaining-days 1461)
  -          (let ((years (min 3 (floor remaining-days 365))))
  +            (floor remaining-days #.(years-to-days 4))
  +          (let ((years (min 3 (floor remaining-days #.(years-to-days 1)))))
               (values (+ (* 400-years 400)
                          (* 100-years 100)
                          (* 4-years 4)
                          years)
  -                    (- remaining-days
  -                       (* years 365))))))))
  +                    (- remaining-days (* years 365))))))))
     ;; the above is the macroexpansion of the following. uses metabang BIND, but kept for clarity because the expansion is unreadable.
     #+nil
     (bind ((remaining-days days)
  
positive.code:         (let ((timezone-transitions
                 ;; read transition times
                 (loop for idx from 1 upto transition-count
                       collect (%read-binary-integer inf 4 t)))
                ;; read local time indexes
                (timestamp-indexes
                 (loop for idx from 1 upto transition-count
                       collect (%read-binary-integer inf 1)))
                ;; read local time info
                (timestamp-info
                 (loop for idx from 1 upto type-count
                       collect (list (%read-binary-integer inf 4 t)
                                     (/= (%read-binary-integer inf 1) 0)
                                     (%read-binary-integer inf 1))))
                ;; read leap second info
                (leap-second-info
                 (loop for idx from 1 upto leap-count
                       collect (list (%read-binary-integer inf 4)
                                     (%read-binary-integer inf 4))))
                (abbreviation-buf (make-array abbrev-length :element-type '(unsigned-byte 8))))
            (read-sequence abbreviation-buf inf :start 0 :end abbrev-length)
            (let ((wall-indicators
                   ;; read standard/wall indicators
                   (loop for idx from 1 upto wall-indicator-count
                         collect (%read-binary-integer inf 1)))
                  ;; read UTC/local indicators
                  (local-indicators
                   (loop for idx from 1 upto utc-indicator-count
                         collect (%read-binary-integer inf 1))))
              (setf (timezone-transitions zone)
                    (nreverse
                     (mapcar
  
negative.code:                     old))
             (forms (list)))
        (%expand-adjust-timestamp-changes old changes
                                          (lambda (change)
                                            (push
                                             `(progn
                                                (multiple-value-bind (nsec sec day)
                                                    ,change
                                                  (setf (nsec-of ,new) nsec)
                                                  (setf (sec-of ,new) sec)
                                                  (setf (day-of ,new) day))
                                                ,@(when functional
                                                        `((setf ,old ,new))))
                                             forms)))
        (setf forms (nreverse forms))
        `(let* ((,old ,timestamp)
                ,@(when functional
  