[tz] Historical fix for Tonga

[Tim Parenti]

First, a quick clerical patch: 0001, attached, fixes the placement of a
comment which got shuffled around in the lead-up to publishing the changes
for South Sudan in 2021a.

Patch 0003 relates to Tonga, and comes from some of the links P Chan shared
to 1957–1963 editions of The Air Almanac:
https://mm.icann.org/pipermail/tz/2021-February/029866.html

On Thu, 25 Feb 2021 at 03:43, P Chan <legco at outlook.com> wrote:

> 1960 Nov (1962.1-4)
> https://books.google.com/books?id=bVgtWM6kPZUC&pg=SL1-PA20
> 1961 Mar (1962.5-8)
> https://books.google.com/books?id=W2nItAul4g0C&pg=SL1-PA20


When looking around at how this data was presented for other regions, I
noticed on the preceding pages (listing "Places Fast on GMT", i.e., east of
Greenwich) in some of the earlier editions provided that Tonga was listed
at GMT+12:20.  The peculiar offset stuck out, and I quickly noticed that
some of the later editions of the same tables had it at GMT+13.

A quick bisection puts the changeover, as far as The Air Almanac
contemporaneously reckoned it, between November 1960 and March 1961.

Previously, our data had Tonga transitioning to UT+13 in 1941 based on a
quotation from a 1997 news article.  Although this differs from what the
Almanac suggests by some 20 years, the article does mention a change
coincident with the New Year, and that Tāufaʻāhau Tupou IV was Crown Prince
at the time.  As his predecessor and mother, Queen Sālote Tupou III,
reigned from 1918-04-05 to 1965-12-16, a possible transition of 1961-01-01
still jives with the gist of the article, even if the specific year was
perhaps wrong or just misprinted.

For what it's worth, our commentary already noted that Shanks & Pottenger
had put the transition even later, at 1968-10-01.  Although of course we
don't know how they arrived at that date, given that they did, 1961 seems
rather less out-of-place than it otherwise might.

The attached patch 0003 makes this adjustment, while more fully documenting
and comparing the conflicting sources.

Thanks again to P Chan for pointing us to these resources.  I wasn't
expecting to get a "bonus" correction out of it, but one never knows quite
what will catch the eye…

--
Tim Parenti
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