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

Paul Eggert eggert at cs.ucla.edu
Sat Jun 13 18:44:19 UTC 2020

On 6/13/20 5:50 AM, Michael H Deckers wrote:

>     the common perception of people about the transition
>     can hardly be determined from a single newspaper report either --

Quite true. It's just one report (and a hypothetical one at that!).

>     However, we _do_ have detailed reports on the switch in French
>     railway time (implying a jump from 00:04:21 to 00:00:00),

The public-facing railway clocks in question didn't jump; they stopped at
00:00:00 for 4 minutes and 21 seconds. The only railway clocks that jumped were
the private watches of the stationmasters, implying that the public-facing
clocks (which everybody else used) recorded the public railway time used by
almost everybody there, with the stationmasters' watches being merely auxiliary
devices to help make sure the public clocks were accurate.

>     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".

Sure, but that does not imply that the radiotelegraph transition was at 00:09:21
old time. On the contrary, the citation you mentioned
<https://gallica.bnf.fr/ark:/12148/bpt6k2022333z/f2> suggests that the
transition was at 00:00 old time.

The cited law says this:

“Art. 2. - Pendant la période s’étendant de la nuit du 10 mars au 11 mars
(minuit), à la nuit du 30 juin au 1er juillet 1911 (minuit), l’indication de
l’heure transmise aux navires en mer, par les stations côtiéres
radiotélègraphiques ouveries au service public, sera suivie de la mention : «
Heure de l’Europe occidentale ».”

which Google Translate renders as:

“[Art. 2. - During the period from the night of March 10 to March 11 (midnight),
to the night of June 30 to July 1, 1911 (midnight), the indication of the time
transmitted to ships at sea, by coastal radio and telegraph stations open to the
public service, will be followed by the words: "Western European Time".]”

As there were at least two legal timestamps equal to “the night of March 10 to
March 11 (midnight)”, this part of the law is arguably ambiguous as to exactly
when radio transmissions started being labeled “Western European Time”. The
intent is clear: they wanted the after-midnight timestamps labeled "Western
European Time" rather than "Paris Mean Time"; but which midnight did they mean?

We have more detail to help us resolve this ambiguity, in the next page of the
cited source, which says “Jusqu’a la nuit du 30 juin 1911 exclusivement, aucune
modification ne sera faite à l’instant de l’envoi des signaux horaires par
l’Observatoire de Paris. [Until the night of June 30, 1911 exclusively, no
modification will be made at the time of the sending of time signals by the
Paris Observatory.]” That is, through June radio time signals were still sent at
the same time intervals as before, with the labels altered to be new time. In
particular, signals were sent daily “La nuit à minuit 0 m. 0 s., minuit 2 m. 0
s., minuit 4 m. 0 s. de temps moyen de Paris [At 00:00:00, 00:02:00, 00:04:00
Paris Mean Time]” with labels “11 h. 50 m. 39 s., 11 h. 52 m. 39 s., 11 h. 54 m.
39 s. [23:50:59, 23:52:39, 23:54:39]”.

We want to know what happened during the change around 1911-03-11 00:00. For
example, were the radio signals sent at 1911-03-11 00:04 old time labeled
“00:04:00 Paris Mean Time” or were they labeled “23:54:39 Western European
Time”? The 1911-03-11 change was supposed to occur from “de la nuit du 10 mars
au 11 mars (minuit)”, which suggests that it was intended to affect the
broadcasts of 00:02 and 00:04 old time as they occurred after midnight old time.
And it would have been odd for the broadcast of 00:00 old time to have been
treated differently from the other two. So this suggests that for the
radiotelegraph, the transition occurred at 00:00 old time.

Of course this is just my reading of the law, and I suppose the law could be
read differently. Had I been running the radiotelegraph I would have said
something like “The time is now 00:00:00 Paris Mean Time, 23:50:39 Western
European Time” for the timestamp sent at midnight old time. This would have
complied with the regulations no matter how they were interpreted, and would
have lessened confusion among receivers of the broadcast.

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