anchor.diff:  
   (eval-when (:compile-toplevel :load-toplevel)
     (defun years-to-days (years)
  +    "Given a number of years, returns the number of days in those years."
       (let* ((days (* years 365))
              (l1 (floor years 4))
              (l2 (floor years 100))
  
positive.code:       (+ days l1 (- l2) l3))))
  
  (defun days-to-years (days)
    "Returns (values years remaining-days-in-year)"
    (let ((remaining-days days))
      (multiple-value-bind (400-years remaining-days)
          (floor remaining-days 146097)
  
negative.code:        1-based-day))))
  
  (defun %timestamp-decode-time (seconds)
    "Returns the hours, minutes, and seconds, given the number of seconds since midnight."
    (declare (type integer seconds))
    (multiple-value-bind (hours hour-remainder)
        (floor seconds +seconds-per-hour+)
  