[racket] Library for date arithmetic?

>
>
> > Does anyone know about a higher-level library for manipulating dates,
> and performing arithmetic comparisons and operations?
>
> Dates are harder than they look.


I absolutely agree with this remark!
Indeed this was the reason I was surprised that (it seems) there is no
high-level date manipulation library, like e.g. Joda Time for Java.


> In this case, for instance, I think it would be a bad idea to add to the
> "day" without checking that the result is a legal date. However, in this
> (and many other) instance(s), it seems like you can get nearly everything
> you want simply by holding off on the "seconds->date" call.
>
> #lang racket
>
> (define DAY-SECONDS 86400)
>
> ;; ALL DATES IN SECONDS:
> (define d   (find-seconds seconds minutes hours day month year))
> (define d+1 (+ d (* 1 DAY-SECONDS)))
> (define d+2 (+ d (* 2 DAY-SECONDS)))
> (define d+3 (+ d (* 3 DAY-SECONDS)))
>
> ;;And then do a comparison, like
>
> (let ([now (current-seconds)])
>    (cond [(< now d) "on time!"]
>          [(< now d+1) "one day late!"]
>          [(< now d+2) "two days late!"]))
>

Thanks, I will implement it this way!
 --
Ismael
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