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

Paul Eggert eggert at cs.ucla.edu
Mon Jun 15 01:17:51 UTC 2020

On 6/14/20 9:08 AM, Michael H Deckers wrote:
>      Is it really so hard to
>      understand that this must have happened when UT was 1911-03-11T00:00:00,
>      and not when UT was 1911-03-10T23:50:39 or 1911-03-10T23:55:39 (or
>      even at different instants for the two time scales)?
This reminds me of the difference between the American way of doing DST
transitions (all transitions are at 02:00 local time) versus the EU way (all
transitions are at 01:00 UTC). The American way is easier to explain to
non-experts, but causes sloppy execution (there are periods where New York is
temporarily the same as Chicago, for example). The EU way is more logical and
has simpler consequences (Paris is always exactly one hour ahead of London), but
is harder to explain to non-experts.

Although the method you're suggesting for the 1911-03-11 French transition is
more logical and has simpler consequences, that doesn't mean it corresponds to
how civil-time clocks behaved or to how people thought they should behave.
Perhaps they thought the transition meant "turn the clocks back at midnight" or
"stop the clocks at midnight" (either of which is easier to specify to
non-experts). At this point we don't really know.

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