Doing date arithmetic with SRFI-19

This may be a fairly evil thing to be doing in the first place, but I've been doing date arithmetic using SRFI-19 like so: 
  
(require (prefix time: ("19.ss" "srfi"))) 
  
(define date-add-days 
  (lambda (dt n) 
     (time:julian-day->date (+ n (time:date->julian-day dt)) 0)))  
  
Now, I can do something like the following: 
> (define next-dt (time:current-date)) 
> (time:date->string next-dt) 
"Thu Aug 05 22:24:58-0600 2004" 
; I'm expecting to get something like "Sun Aug 08 22:24:58-0600 2004" 
> (set! next-dt (date-add-days next-dt 3)) 
* remainder: expects type <integer> as 1st argument, given: 9827308833624167200/9; other arguments were: 1000000000 

The thing is, this works using the 1.3 SRFI release, somehow, but when I got a new version of SRFI from CVS this now is broken.  Any suggestions on what the right way to do this would be? 
-- 
Gordon Weakliem 
http://www.eighty-twenty.net 


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