anchor.diff:      (let* ((leap-day-p (= remaining-days 365))
              (rotated-1-based-month (if leap-day-p
                                         12 ; march is the first month and february is the last
  -                                      (position remaining-days #.+rotated-month-offsets-without-leap-day+ :test #'<)))
  +                                      (position remaining-days +rotated-month-offsets-without-leap-day+ :test #'<)))
              (1-based-month (if (>= rotated-1-based-month 11)
                                 (- rotated-1-based-month 10)
                                 (+ rotated-1-based-month 2)))
              (1-based-day (if leap-day-p
                               29
  -                            (1+ (- remaining-days (aref #.+rotated-month-offsets-without-leap-day+
  +                            (1+ (- remaining-days (aref +rotated-month-offsets-without-leap-day+
                                                           (1- rotated-1-based-month)))))))
         (values
          (+ years
  
positive.code:            (day (day-of time)))
         (case part
           (:nsec (setf nsec (coerce new-value '(integer 0 999999999))))
           (:sec-of-day (setf sec (coerce new-value '(integer 0 #.+seconds-per-day+))))
           (:day (setf day new-value)))
         (values nsec sec day)))
      (otherwise
  
negative.code:                  (* minute +seconds-per-minute+)
                   sec))
           (days-from-zero-point (+ years-as-days
                                    (aref +rotated-month-offsets-without-leap-day+ 0-based-rotated-month)
                                    (1- day))))
      (multiple-value-bind (utc-sec utc-day)
          (%adjust-to-offset sec days-from-zero-point (- offset))
  