[tz] Large scale changes proposed in 2014f

Paul Eggert 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:
> https://github.com/jodastephen/tzdiff/commit/c812da9e12bd6f8aa52fa2dd758e236581c23a29

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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