[tz] Fwd: DST changes in Hungary (full historical revision)

[Arthur David Olson]

 > Anyway, the bottom line is that the stopped clocks make this an oddball
transition that cannot be modeled exactly by tzdb

Unless you're willing to have a slew of one-second-apart transitions with
each one differing from its neighbor by one second.-)

    @dashdashado

On Wed, Jun 10, 2020 at 5:25 PM Paul Eggert <eggert at cs.ucla.edu> wrote:

> Thanks for the heads-up. I also found a contemporaneous English-language
> source,
> the Brooklyn Daily Eagle Almanac (1912).
>
> Unfortunately, we have no good way to model stopped clocks in tzdb, as tzdb
> clocks are always running. So we need a transition of some sort, presumably
> either one like 2020a (from 00:01:00 local time to 23:51:39 the previous
> day),
> or the other, more-logical one (from 00:09:21 local time to 00:00:00 the
> same day).
>
> Now that I'm looking into it, the line "0:09:21 - PMT 1911 Mar 11 0:01 #
> Paris
> MT" that's currently in tzdb is surely a typo. It's not what's in Shanks,
> who
> gives a transition time of "0:00". Formerly tzdb had no time for that
> transition, which defaulted the time to 00:00. My patch dated 2001-03-13
> changed
> this to "0:01", but this part of the patch patch was in response to an
> email
> dated 2000-12-20 (or -19) from Ciro Disceopolo
> <https://mm.icann.org/pipermail/tz/2000-December/011284.html> which says
> nothing
> about that "0:01". Evidently I mistakenly copied the "0:01" from the
> previous
> line "Zone Europe/Paris 0:09:21 - LMT 1891 Mar 15 0:01", where Shanks does
> say
> "0:01".
>
> Anyway, the bottom line is that the stopped clocks make this an oddball
> transition that cannot be modeled exactly by tzdb, and that given the
> story you
> mentioned you are correct that it's better modeled using an ordinary
> transition
> (from 00:09:21 to 00:00:00) than the unusual transition we're currently
> using. I
> installed the attached proposed patch into the development database.
>
> Given the above, we have a new trivia question: when and where could a
> stopped
> clock have been correct *more* than three times in a single day? Answer: a
> clock
> stopped at 00:00 was correct an infinite number of times that day in
> France.
>
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