Ah, great, thanks!

I have been looking at the wrong node all the time.

However, the manual node you're pointing to disagrees with the claim that
those are equivalent:

>If you need both a repeater and a special warning period in a deadline
>entry, the repeater should come first and the warning period last
>     DEADLINE: <2005-10-01 Sat +1m -3d>

However, the manual may be incomplete.

Thank you, problem seems to be solved.

Kyle Meyer <kyle@kyleam.com> 於 2020年4月30日 週四 13:02 寫道：

> Vladimir Nikishkin <lockywolf@gmail.com> writes:
>
> > I need to pay a fee by every 28th of the month, and I want this task
> > to show up in the agenda from the 20th of the next not paid month.
> >
> > What's the proper DEADLINE  format?
> >
> > DEADLINE: <2020-02-28 Sun .+1m -10d>  ?
> > DEADLINE: <2020-02-28 Sun -10d .+1m>  ?
>
> Those are equivalent.  Though you might consider whether you'd prefer
> '+' or '++' for this rather than '.+'.  See (info "(org)Repeated tasks")
> if you're not aware of the differences.
>
> And note that a utility like datefudge or libfaketime is useful for
> testing these sorts of things out.  For example:
>
>   $ datefudge "2020-02-18" emacs [...]
>