Diff between two dates

[Peter58]

Hi all . I'm an absolute beginner in NIM :-)

let now1 = format(now(), "dd/MM/yyyy")

let debut = parse("04-09-2019", "dd-MM-yyyy") echo debut.format("dd-MM-yyyy")

I would to obtain the result (in number of Days) between these two dates ! 
Thanks a lot, in advance...