Re: More tzdb fun: POSIXRULES is being deprecated upstream

On Thu, Jun 18, 2020 at 1:05 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > It's a little confusing, though, that you documented it as Mm.n.d but
> > then in the text the order of explanation is d then m then n. Maybe
> > switch the text around so the order matches, or even use something
> > like Mmonth.occurrence.day.
>
> Yeah, I struggled with that text for a bit. It doesn't seem to make sense
> to explain that n means the n'th occurrence of a particular d value before
> we've explained what d is, so explaining the fields in their syntactic
> order seems like a loser. But we could describe m first without that
> problem.

You could consider something along the lines of:

This form specifies a transition that always happens during the same
month and on the same day of the week. m identifies the month, from 1
to 12. n specifies the n'th occurrence of the day number identified by
d. n is a value between 1 and 4, or 5 meaning the last occurrence of
that weekday in the month (which could be the fourth or the fifth). d
is a value between 0 and 6, with 0 indicating Sunday.

--
Robert Haas
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