[tz] Some time zone history (2)

[Tim Parenti]

On Fri, 27 Nov 2020 at 07:04, P Chan <legco at outlook.com> wrote:

> Vanuatu
>
> DST was observed in 1973/1974. The spring forward in 1984 should be on Sep
> 23.


Thanks; I've installed the attached patch.  The early Tuesday morning
transition we'd previously had on 23 October 1984 was certainly suspect.

It is notable that the effective times of the 1973/1974 changes were given
as "twelve o'clock midday, Greenwich mean time"; of course this would be
late in the evening in the region.

Transitions in the 1983–1993 period were all given as taking effect "at
midnight local time on the fourth Saturday" (in the French, "à minuit,
heure locale le quatrième samedi"), which mostly matches with our previous
data if taken to mean 24:00, which makes sense given context.  I used
"Sat>=22 24:00" to simplify the September transitions in 1983–1991, and
carried this notation forward to the others to better match the
legislation, although it doesn't change any other transitions (which we had
as the equivalent "Sun>=23 0:00").

--
Tim Parenti
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