anchor.diff:             #:days-in-month
              #:modified-local-time
              #:adjusted-local-time
  +           #:local-time-
  +           #:local-time+
  +           #:encode-duration
              #:maximize-time-part
              #:minimize-time-part
              #:first-day-of-year
  
positive.code: (defun modified-julian-date (local-time)
    (- (day-of local-time) +modified-julian-date-offset+))
  
  (defun local-time-diff (time-a time-b)
    "Returns a new LOCAL-TIME containing the difference between TIME-A and TIME-B"
    (multiple-value-bind (day-a sec-a)
        (local-time-adjust time-a (timezone-of time-b))
        (let ((nsec (- (nsec-of time-a) (nsec-of time-b)))
              (seconds (- sec-a (sec-of time-b)))
              (days (- day-a (day-of time-b))))
          (when (minusp nsec)
            (decf seconds)
            (incf nsec 1000000000))
          (when (minusp seconds)
            (decf days)
            (incf seconds 86400))
          (make-local-time :nsec nsec
                           :sec seconds
                           :day days))))
  
  (defun local-time-sum (time-a time-b)
    "Returns a new LOCAL-TIME containing the sum of TIME-A and TIME-B"
  
negative.code:            #:+minutes-per-day+
             #:+minutes-per-hour+
             #:+hours-per-day+
             #:+days-per-week+
             #:astronomical-julian-date
             #:modified-julian-date
             #:astronomical-modified-julian-date))
  