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.
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 [...]