RE: 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:

It's not SRFI-19, but FWIW, I've used something even more evil (no
guarantees, it's not being used in anything mission-critical):

;; routines to support calendar dates with no time info
(require (lib "date.ss"))

;; adds support for (make-date year month day)
(define make-date
  (let ((sys-make-date make-date))
    (lambda args
      (if (= (length args) 3)
          (seconds->date (apply find-seconds 0 0 0 (reverse args)))
          (apply sys-make-date args)))))

(define (date->seconds date)
  (find-seconds 0 0 0 (date-day date) (date-month date) (date-year date)))

(define (days-between first-date last-date)
  (/ (- (date->seconds last-date) (date->seconds first-date)) 24 60 60))

(define (date+ date days)
  (seconds->date (+ (date->seconds date) (* days 24 60 60))))



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