[tz] Large scale changes proposed in 2014f
eggert at cs.ucla.edu
Fri Aug 1 00:20:52 UTC 2014
Stephen Colebourne wrote:
> The differences between 2014e and 2014f-proposed can be seen here:
You can also see changes directly from the experimental version, using
URLs like this:
I don't normally use a web-based interface, though; I use 'git'
directly. For example, on my development host the shell command 'git
diff 2014e' outputs a text file containing all the changes since 2014e.
> - Africa/Accra gains DST between 1920 and 1935
Yes, this is a result of integrating a better source, one that appears
to be more reliable than Shanks & Pottenger, namely Scott Keltie &
Epstein 1920. The new source is more contemporaneous and is from a
reasonably respectable publisher, and is more trustworthy than Shanks &
> - Africa/Freetown loses its entire history of DST
The old entry was taken from Shanks & Pottenger, but it's so dubious
that it cannot be right. Not only does it disagree with Whitman, it
also disagrees with the The International Hydrographic Bulletin,
1932-33, p 63. One possible explanation is that Shanks entered some
data with a reversed sign (thus confusing a DST of 20 minutes with a DST
of 40 minutes from the preceding time zone), which would mean that a
reasonably-sized chunk of 2014e is an hour off. Without further
information we're better off omitting this dubious data entirely.
> Asia/Urumqi loses its entire history.
Not all the history, just the post-1980 transitions to Beijing time, as
Urumqi now uses Xinjiang time. This is due to reports by Luther Ma and
from Guo Qingshen (via Alois Triendl) that have been discussed on the
list. The data from Shanks & Pottenger are obviously wrong for Xinjiang
time, and the new data are closer to being correct. I write "closer"
because we do not know what happened in Ürümqi during the warlord rule
in the 20th century -- but that part of the history has been retained.
For the remaining changes you mentioned, where we lack data, your
summary greatly exaggerates the extent of the changes. For example,
it's simply not true that Ho Chi Minh City loses its "entire history":
all its time stamps since 1931 are unchanged, and even some of the time
stamps before then are the same as before. All that's removed are two
or three questionable transitions before 1932, transitions for which we
have no reliable source.
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