[tz] Historical fix for Tonga

Michael H Deckers michael.h.deckers at googlemail.com
Wed Mar 3 16:10:33 UTC 2021

    On 2021-03-03 03:59, Tim Parenti via tz wrote:

> 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.

      While you are at it, let me quote

        [Ian R Bartky: "One Time Fits All: The Campaigns for Global 
        Stanford University Press. 2007. p 24..26]:

            3. On 10 September 1945 Tonga adopted a standard time 12 hours,
            20 minutes in advance of Greenwich. On 19 October 1960 the
            legislation was amended by shifting to a time 13 hours in
            advance, and continuing the Eastern reckoning of the days.
            Tonga's daylight saving time, observed in 1999 and 2000,
            was abandoned by 2002. I thank Rhys Richards for these dates.

      This implies that tzdb is wrong for Tonga at least from 1945-09-10
      until 1960-10-19, and it is compatible with your proposal for the
      switch to UT + 13:00 at 1961-01-01. And it suggests that the switch
      from LMT to UT + 12:20 should be advanced from 1901 to 1945-09-10.

      Michael Deckers.

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