[tz] Hong Kong time 1941

[Michael H Deckers]

     On 2018-11-18 20:04, Paul Eggert wrote:


> However, Hong Kong switched at 17:00 UT so if the intent was for Macau 
> to keep in lock-step with Hong Kong, the Macau transition should be at 
> 17:00 UT.
>



   But we simply do not have any evidence that "Hong Kong switched at 
17:00 UT".

   Steve Allen has shown that the documents available for Hong Kong only 
show
   that the time ball was flown (and a cannon was shot) when UT was 
1904-10-30T05
   (and GMT was 1904-10-29T17). That happened 12 h after your proposed 
switch
   of Hong Kong time to UT + 08 h. We just do not seem to have any new
   evidence for the switch of Hong Kong time in 1904.

   But we do have evidence that Macau switched to UT + 08 h when UT was
   1904-10-29T16 (tzdb currently says, 1904-10-29T16:23:18), and
   that they did that in order to achieve a common time scale with the
   neighboring parts of China.

   I do not want to pester the list with my quibbles about your proposed
   changes, and this will be my last post on this issue -- I just want
   to make sure that tzdb makes the most proficient use of the aggregated
   knowledge of the people in this list.

   Portaria N° 204 of 1904-10-21 for Macau was announced by P Chan on 
2018-05-10
   and it was rightly noted in tzdb that this indicated the switch to a 
common
   time scale with Hong Kong. The new documents for Hong Kong do not
   change this view (otherwise the text of tzdb would have to be corrected
   anyway). For all we know, it is likely that Macau and Hong Kong switched
   to UT + 08 h at the same instant (and that instant most likely was when
   UT was 1904-10-29T16).

   Michael Deckers.