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

Michael H Deckers michael.h.deckers at googlemail.com
Sat Jun 13 12:50:15 UTC 2020

    On 2020-06-12 21:42, Paul Eggert wrote:

> But this is curious, as that story also makes sense only if clocks were set back
> at 00:00 "old time" - which is not what I installed yesterday in tzdb master
> where clocks were set back at 00:09:21 "old time" so there was no difficulty
> with the unfortunate hypothetical children in question.

     Yes, the offset is wrong and so is the instant implied for the jump.
     A single sentence in a contemporary newspaper should not be taken
     at face value, especially if some arithmetic is involved.

> This new citation suggests that it was more common for people to think of clocks
> as being set back at midnight old time, which means we should revert to tzdb
> 2020a practice (while keeping the other changes you've suggested).

     Well, the common perception of people about the transition
     can hardly be determined from a single newspaper report either --
     but common sense tells us that most people did not care a bit
     about whether the jump was from 00:09:21 to 00:00:00 or
     from 00:00:00 to 23:50:39 (or anything in between).

     However, we _do_ have detailed reports on the switch in French
     railway time (implying a jump from 00:04:21 to 00:00:00), and we
     know that radio signals since 1911-03-11T00:00:00 (not since
     1911-03-10T23:50:39) were ordered to be transmitted with the
     label "heure nouvelle". This is, in my opinion, evidence
     that the switch in French legal time occurred when UT was

> In other words, since the law doesn't specify how the transition occurred, if actual
> practice varied and some people switched at midnight old-time, then tzdb should
> leave the time blank (defaulting to 00:00) to hint that "0:00" would be
> overspecifying.

     I do not know whether I have seen all legal texts about
     the switch. The switch in railway time seems to have been
     planned meticulously, and there are references to additional
     legal texts concerning the switch which I have not found.

     Michael Deckers.

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